ESP32-S2 ULP coprocessor instruction set
This document provides details about the instructions used by ESP32-S2 ULP FSM coprocessor assembler.
ULP FSM coprocessor has 4 16-bit general purpose registers, labeled R0, R1, R2, R3. It also has an 8-bit counter register (stage_cnt) which can be used to implement loops. Stage count register is accessed using special instructions.
ULP coprocessor can access 8k bytes of RTC_SLOW_MEM memory region. Memory is addressed in 32-bit word units. It can also access peripheral registers in RTC_CNTL, RTC_IO, and SENS peripherals.
All instructions are 32-bit. Jump instructions, ALU instructions, peripheral register and memory access instructions are executed in 1 cycle. Instructions which work with peripherals (TSENS, ADC, I2C) take variable number of cycles, depending on peripheral operation.
The instruction syntax is case insensitive. Upper and lower case letters can be used and intermixed arbitrarily. This is true both for register names and instruction names.
Note about addressing
ESP32-S2 ULP FSM coprocessor's JUMP, ST, LD family of instructions expect the address argument to be expressed in the following way depending on the type of address argument used:
When the address argument is presented as a label then the instruction expects the address to be expressed as 32-bit words.
Consider the following example program:
entry: NOP NOP NOP NOP loop: MOVE R1, loop JUMP R1
When this program is assembled and linked, address of label
loopwill be equal to 16 (expressed in bytes). However JUMP instruction expects the address stored in registerR1to be expressed in 32-bit words. To account for this common use case, the assembler will convert the address of label loop from bytes to words, when generating theMOVEinstruction. Hence, the code generated code will be equivalent to:0000 NOP 0004 NOP 0008 NOP 000c NOP 0010 MOVE R1, 4 0014 JUMP R1
The other case is when the argument of
MOVEinstruction is not a label but a constant. In this case assembler will use the value as is, without any conversion:.set val, 0x10 MOVE R1, val
In this case, value loaded into
R1will be0x10.However, when an immediate value is used as an offset in
LDandSTinstructions, the assembler considers the address argument in bytes and converts it to 32-bit words before executing the instruction:ST R1, R2, 4 // offset = 4 bytes; Mem[R2 + 4 / 4] = R1
In this case, the value in R1 is stored at the memory location pointed by [R2 + offset / 4]
Consider the following code:
.global array array: .long 0 .long 0 .long 0 .long 0 MOVE R1, array MOVE R2, 0x1234 ST R2, R1, 0 // write value of R2 into the first array element, // i.e. array[0] ST R2, R1, 4 // write value of R2 into the second array element // (4 byte offset), i.e. array[1] ADD R1, R1, 2 // this increments address by 2 words (8 bytes) ST R2, R1, 0 // write value of R2 into the third array element, // i.e. array[2]
Note about instruction execution time
ULP coprocessor is clocked from RTC_FAST_CLK, which is normally derived from the internal 8MHz oscillator. Applications which need to know exact ULP clock frequency can calibrate it against the main XTAL clock:
#include "soc/rtc.h"
// calibrate 8M/256 clock against XTAL, get 8M/256 clock period
uint32_t rtc_8md256_period = rtc_clk_cal(RTC_CAL_8MD256, 100);
uint32_t rtc_fast_freq_hz = 1000000ULL * (1 << RTC_CLK_CAL_FRACT) * 256 / rtc_8md256_period;
ULP coprocessor needs certain number of clock cycles to fetch each instruction, plus certain number of cycles to execute it, depending on the instruction. See description of each instruction below for details on the execution time.
Instruction fetch time is:
2 clock cycles — for instructions following ALU and branch instructions.
4 clock cycles — in other cases.
Note that when accessing RTC memories and RTC registers, ULP coprocessor has lower priority than the main CPUs. This means that ULP coprocessor execution may be suspended while the main CPUs access same memory region as the ULP.
The detailed description of all instructions is presented below:
Difference between ESP32 ULP and ESP32-S2 ULP Instruction sets
Compared to the ESP32 ULP FSM coprocessor, the ESP32-S2 ULP FSM coprocessor has an extended instruction set. The ESP32-S2 ULP FSM is not binary compatible with ESP32 ULP FSM,
but a ESP32 ULP FSM assembled program is expected to work on the ESP32-S2 ULP FSM after rebuilding.
The list of the new instructions that was added to the ESP32-S2 ULP FSM is: LDL, LDH, STL, STH, ST32, STO, STI, STI32.
NOP - no operation
- Syntax
NOP
- Operands
None
- Cycles
2 cycle to execute, 4 cycles to fetch next instruction
- Description
No operation is performed. Only the PC is incremented.
Example:
1: NOP
ADD - Add to register
- Syntax
ADD Rdst, Rsrc1, Rsrc2
ADD Rdst, Rsrc1, imm
- Operands
Rdst - Register R[0..3]
Rsrc1 - Register R[0..3]
Rsrc2 - Register R[0..3]
Imm - 16-bit signed value
- Cycles
2 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction adds source register to another source register or to a 16-bit signed value and stores the result in the destination register.
Examples:
1: ADD R1, R2, R3 // R1 = R2 + R3
2: Add R1, R2, 0x1234 // R1 = R2 + 0x1234
3: .set value1, 0x03 // constant value1=0x03
Add R1, R2, value1 // R1 = R2 + value1
4: .global label // declaration of variable label
add R1, R2, label // R1 = R2 + label
...
label: nop // definition of variable label
SUB - Subtract from register
- Syntax
SUB Rdst, Rsrc1, Rsrc2
SUB Rdst, Rsrc1, imm
- Operands
Rdst - Register R[0..3]
Rsrc1 - Register R[0..3]
Rsrc2 - Register R[0..3]
Imm - 16-bit signed value
- Cycles
2 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction subtracts the source register from another source register or subtracts a 16-bit signed value from a source register, and stores the result to the destination register.
Examples:
1: SUB R1, R2, R3 // R1 = R2 - R3
2: sub R1, R2, 0x1234 // R1 = R2 - 0x1234
3: .set value1, 0x03 // constant value1=0x03
SUB R1, R2, value1 // R1 = R2 - value1
4: .global label // declaration of variable label
SUB R1, R2, label // R1 = R2 - label
....
label: nop // definition of variable label
AND - Bitwise logical AND of two operands
- Syntax
AND Rdst, Rsrc1, Rsrc2
AND Rdst, Rsrc1, imm
- Operands
Rdst - Register R[0..3]
Rsrc1 - Register R[0..3]
Rsrc2 - Register R[0..3]
Imm - 16-bit signed value
- Cycles
2 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction does a bitwise logical AND of a source register and another source register or a 16-bit signed value and stores the result to the destination register.
Examples:
1: AND R1, R2, R3 // R1 = R2 & R3
2: AND R1, R2, 0x1234 // R1 = R2 & 0x1234
3: .set value1, 0x03 // constant value1=0x03
AND R1, R2, value1 // R1 = R2 & value1
4: .global label // declaration of variable label
AND R1, R2, label // R1 = R2 & label
...
label: nop // definition of variable label
OR - Bitwise logical OR of two operands
- Syntax
OR Rdst, Rsrc1, Rsrc2
OR Rdst, Rsrc1, imm
- Operands
Rdst - Register R[0..3]
Rsrc1 - Register R[0..3]
Rsrc2 - Register R[0..3]
Imm - 16-bit signed value
- Cycles
2 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction does a bitwise logical OR of a source register and another source register or a 16-bit signed value and stores the result to the destination register.
Examples:
1: OR R1, R2, R3 // R1 = R2 || R3
2: OR R1, R2, 0x1234 // R1 = R2 || 0x1234
3: .set value1, 0x03 // constant value1=0x03
OR R1, R2, value1 // R1 = R2 || value1
4: .global label // declaration of variable label
OR R1, R2, label // R1 = R2 || label
...
label: nop // definition of variable label
LSH - Logical Shift Left
- Syntax
LSH Rdst, Rsrc1, Rsrc2
LSH Rdst, Rsrc1, imm
- Operands
Rdst - Register R[0..3]
Rsrc1 - Register R[0..3]
Rsrc2 - Register R[0..3]
Imm - 16-bit signed value
- Cycles
2 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction does a logical shift to left of the source register by the number of bits from another source register or a 16-bit signed value and stores the result to the destination register.
Note
Shift operations which are greater than 15 bits will have an undefined result.
Examples:
1: LSH R1, R2, R3 // R1 = R2 << R3
2: LSH R1, R2, 0x03 // R1 = R2 << 0x03
3: .set value1, 0x03 // constant value1=0x03
LSH R1, R2, value1 // R1 = R2 << value1
4: .global label // declaration of variable label
LSH R1, R2, label // R1 = R2 << label
...
label: nop // definition of variable label
RSH - Logical Shift Right
- Syntax
RSH Rdst, Rsrc1, Rsrc2
RSH Rdst, Rsrc1, imm
- Operands
Rdst - Register R[0..3] Rsrc1 - Register R[0..3] Rsrc2 - Register R[0..3] Imm - 16-bit signed value
- Cycles
2 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction does a logical shift to right of a source register by the number of bits from another source register or a 16-bit signed value and stores the result to the destination register.
Note
Shift operations which are greater than 15 bits will have an undefined result.
Examples:
1: RSH R1, R2, R3 // R1 = R2 >> R3
2: RSH R1, R2, 0x03 // R1 = R2 >> 0x03
3: .set value1, 0x03 // constant value1=0x03
RSH R1, R2, value1 // R1 = R2 >> value1
4: .global label // declaration of variable label
RSH R1, R2, label // R1 = R2 >> label
label: nop // definition of variable label
MOVE – Move to register
- Syntax
MOVE Rdst, Rsrc
MOVE Rdst, imm
- Operands
Rdst – Register R[0..3]
Rsrc – Register R[0..3]
Imm – 16-bit signed value
- Cycles
2 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction moves the value from the source register or a 16-bit signed value to the destination register.
Note
Note that when a label is used as an immediate, the address of the label will be converted from bytes to words. This is because LD, ST, and JUMP instructions expect the address register value to be expressed in words rather than bytes. See the section Note about addressing for more details.
Examples:
1: MOVE R1, R2 // R1 = R2
2: MOVE R1, 0x03 // R1 = 0x03
3: .set value1, 0x03 // constant value1=0x03
MOVE R1, value1 // R1 = value1
4: .global label // declaration of label
MOVE R1, label // R1 = address_of(label) / 4
...
label: nop // definition of label
ST – Store data to the memory
- Syntax
ST Rsrc, Rdst, offset
- Operands
Rsrc – Register R[0..3], holds the 16-bit value to store
Rdst – Register R[0..3], address of the destination, in 32-bit words
Offset – 13-bit signed value, offset in bytes
- Cycles
4 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction stores the 16-bit value of Rsrc to the lower half-word of memory with address Rdst+offset. The upper half-word is written with the current program counter (PC) (expressed in words, shifted left by 5 bits) OR'd with Rdst (0..3):
Mem[Rdst + offset / 4]{31:0} = {PC[10:0], 3'b0, Rdst, Rsrc[15:0]}
The application can use the higher 16 bits to determine which instruction in the ULP program has written any particular word into memory.
Note
Note that the offset specified in bytes is converted to a 32-bit word offset before execution. See the section Note about addressing for more details.
Examples:
1: ST R1, R2, 0x12 // MEM[R2 + 0x12 / 4] = R1
2: .data // Data section definition
Addr1: .word 123 // Define label Addr1 16 bit
.set offs, 0x00 // Define constant offs
.text // Text section definition
MOVE R1, 1 // R1 = 1
MOVE R2, Addr1 // R2 = Addr1
ST R1, R2, offs // MEM[R2 + 0 / 4] = R1
// MEM[Addr1 + 0] will be 32'h600001
STL – Store data to the lower 16 bits of 32-bit memory
- Syntax
STL Rsrc, Rdst, offset, Label
- Operands
Rsrc – Register R[0..3], holds the 16-bit value to store
Rdst – Register R[0..3], address of the destination, in 32-bit words
Offset – 11-bit signed value, offset in bytes
Label – 2-bit user defined unsigned value
- Cycles
4 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction stores the 16-bit value of Rsrc to the lower half-word of the memory with address [Rdst + offset / 4]:
Mem[Rdst + offset / 4]{15:0} = {Rsrc[15:0]} Mem[Rdst + offset / 4]{15:0} = {Label[1:0],Rsrc[13:0]}
The
STand theSTLcommands can be used interchangeably and have been provided to maintain backward compatibility with previous versions of the ULP core.
Note
Note that the offset specified in bytes is converted to a 32-bit word offset before execution. See the section Note about addressing for more details.
Examples:
1: STL R1, R2, 0x12 // MEM[R2 + 0x12 / 4] = R1
2: .data // Data section definition
Addr1: .word 123 // Define label Addr1 16 bit
.set offs, 0x00 // Define constant offs
.text // Text section definition
MOVE R1, 1 // R1 = 1
MOVE R2, Addr1 // R2 = Addr1
STL R1, R2, offs // MEM[R2 + 0 / 4] = R1
// MEM[Addr1 + 0] will be 32'hxxxx0001
3:
MOVE R1, 1 // R1 = 1
STL R1, R2, 0x12, 1 // MEM[R2 + 0x12 / 4] = 0xxxxx4001
STH – Store data to the higher 16 bits of 32-bit memory
- Syntax
STH Rsrc, Rdst, offset, Label
- Operands
Rsrc – Register R[0..3], holds the 16-bit value to store
Rdst – Register R[0..3], address of the destination, in 32-bit words
Offset – 11-bit signed value, offset in bytes
Label – 2-bit user defined unsigned value
- Cycles
4 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction stores the 16-bit value of Rsrc to the upper half-word of memory with address [Rdst + offset / 4]:
Mem[Rdst + offset / 4]{31:16} = {Rsrc[15:0]} Mem[Rdst + offset / 4]{31:16} = {Label[1:0],Rsrc[13:0]}
Note
Note that the offset specified in bytes is converted to a 32-bit word offset before execution. See the section Note about addressing for more details.
Examples:
1: STH R1, R2, 0x12 // MEM[R2 + 0x12 / 4][31:16] = R1
2: .data // Data section definition
Addr1: .word 123 // Define label Addr1 16 bit
.set offs, 0x00 // Define constant offs
.text // Text section definition
MOVE R1, 1 // R1 = 1
MOVE R2, Addr1 // R2 = Addr1
STH R1, R2, offs // MEM[R2 + 0 / 4] = R1
// MEM[Addr1 + 0] will be 32'h0001xxxx
3:
MOVE R1, 1 // R1 = 1
STH R1, R2, 0x12, 1 // MEM[R2 + 0x12 / 4] 0x4001xxxx
ST32 – Store 32-bits data to the 32-bits memory
- Syntax
ST32 Rsrc, Rdst, offset, Label
- Operands
Rsrc – Register R[0..3], holds the 16-bit value to store
Rdst – Register R[0..3], address of the destination, in 32-bit words
Offset – 11-bit signed value, offset in bytes
Label – 2-bit user defined unsigned value
- Cycles
4 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction stores 11 bits of the PC value, label value and the 16-bit value of Rsrc to the 32-bit memory with address [Rdst + offset / 4]:
Mem[Rdst + offset / 4]{31:0} = {PC[10:0],0[2:0],Label[1:0],Rsrc[15:0]}
Note
Note that the offset specified in bytes is converted to a 32-bit word offset before execution. See the section Note about addressing for more details.
Examples:
1: ST32 R1, R2, 0x12, 0 // MEM[R2 + 0x12 / 4][31:0] = {PC[10:0],0[2:0],Label[1:0],Rsrc[15:0]}
2: .data // Data section definition
Addr1: .word 123 // Define label Addr1 16 bit
.set offs, 0x00 // Define constant offs
.text // Text section definition
MOVE R1, 1 // R1 = 1
MOVE R2, Addr1 // R2 = Addr1
ST32 R1, R2, offs, 1 // MEM[R2 + 0] = {PC[10:0],0[2:0],Label[1:0],Rsrc[15:0]}
// MEM[Addr1 + 0] will be 32'h00010001
STO – Set offset value for auto increment operation
- Syntax
STO offset
- Operands
Offset – 11-bit signed value, offset in bytes
- Cycles
4 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction sets the 16-bit value to the offset register:
offset = value / 4
Note
Note that the offset specified in bytes is converted to a 32-bit word offset before execution. See the section Note about addressing for more details.
Examples:
1: STO 0x12 // Offset = 0x12 / 4
2: .data // Data section definition
Addr1: .word 123 // Define label Addr1 16 bit
.set offs, 0x00 // Define constant offs
.text // Text section definition
STO offs // Offset = 0x00
STI – Store data to the 32-bits memory with auto increment of predefined offset address
- Syntax
STI Rsrc, Rdst, Label
- Operands
Rsrc – Register R[0..3], holds the 16-bit value to store
Rdst – Register R[0..3], address of the destination, in 32-bit words
Label – 2-bit user defined unsigned value
- Cycles
4 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction stores the 16-bit value of Rsrc to the lower and upper half-word of memory with address [Rdst + offset / 4]. The offset value is auto incremented when the STI instruction is called twice. Make sure to execute the
STOinstruction to set the offset value before executing the STI instruction:Mem[Rdst + offset / 4]{15:0/31:16} = {Rsrc[15:0]} Mem[Rdst + offset / 4]{15:0/31:16} = {Label[1:0],Rsrc[13:0]}
Examples:
1: STO 4 // Set offset to 4
STI R1, R2 // MEM[R2 + 4 / 4][15:0] = R1
STI R1, R2 // MEM[R2 + 4 / 4][31:16] = R1
// offset += (1 * 4) //offset is incremented by 1 word
STI R1, R2 // MEM[R2 + 8 / 4][15:0] = R1
STI R1, R2 // MEM[R2 + 8 / 4][31:16] = R1
STI32 – Store 32-bits data to the 32-bits memory with auto increment of adress offset
- Syntax
STI32 Rsrc, Rdst, Label
- Operands
Rsrc – Register R[0..3], holds the 16-bit value to store
Rdst – Register R[0..3], address of the destination, in 32-bit words
Label – 2-bit user defined unsigned value
- Cycles
4 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction stores 11 bits of the PC value, label value and the 16-bit value of Rsrc to the 32-bit memory with address [Rdst + offset / 4]. The offset value is auto incremented each time the STI32 instruction is called. Make sure to execute the
STOinstruction to set the offset value before executing the STI32 instruction:Mem[Rdst + offset / 4]{31:0} = {PC[10:0],0[2:0],Label[1:0],Rsrc[15:0]}
Examples:
1: STO 0x12
STI32 R1, R2, 0 // MEM[R2 + 0x12 / 4][31:0] = {PC[10:0],0[2:0],Label[1:0],Rsrc[15:0]}
// offset += (1 * 4) //offset is incremented by 1 word
STI32 R1, R2, 0 // MEM[R2 + 0x16 / 4][31:0] = {PC[10:0],0[2:0],Label[1:0],Rsrc[15:0]}
LD – Load data from the memory
- Syntax
LD Rdst, Rsrc, offset
- Operands
Rdst – Register R[0..3], destination
Rsrc – Register R[0..3], holds address of destination, in 32-bit words
Offset – 13-bit signed value, offset in bytes
- Cycles
4 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction loads the lower 16-bit half-word from memory with address [Rsrc + offset / 4] into the destination register Rdst:
Rdst[15:0] = Mem[Rsrc + offset / 4][15:0]
Note
Note that the offset specified in bytes is converted to a 32-bit word offset before execution. See the section Note about addressing for more details.
Examples:
1: LD R1, R2, 0x12 // R1 = MEM[R2 + 0x12 / 4]
2: .data // Data section definition
Addr1: .word 123 // Define label Addr1 16 bit
.set offs, 0x00 // Define constant offs
.text // Text section definition
MOVE R1, 1 // R1 = 1
MOVE R2, Addr1 // R2 = Addr1 / 4 (address of label is converted into words)
LD R1, R2, offs // R1 = MEM[R2 + 0]
// R1 will be 123
LDL – Load data from the lower half-word of the 32-bit memory
- Syntax
LDL Rdst, Rsrc, offset
- Operands
Rdst – Register R[0..3], destination
Rsrc – Register R[0..3], holds address of destination, in 32-bit words
Offset – 13-bit signed value, offset in bytes
- Cycles
4 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction loads the lower 16-bit half-word from memory with address [Rsrc + offset / 4] into the destination register Rdst:
Rdst[15:0] = Mem[Rsrc + offset / 4][15:0]
The
LDand theLDLcommands can be used interchangeably and have been provided to maintain backward compatibility with previous versions of the ULP core.
Note
Note that the offset specified in bytes is converted to a 32-bit word offset before execution. See the section Note about addressing for more details.
Examples:
1: LDL R1, R2, 0x12 // R1 = MEM[R2 + 0x12 / 4]
2: .data // Data section definition
Addr1: .word 123 // Define label Addr1 16 bit
.set offs, 0x00 // Define constant offs
.text // Text section definition
MOVE R1, 1 // R1 = 1
MOVE R2, Addr1 // R2 = Addr1 / 4 (address of label is converted into words)
LDL R1, R2, offs // R1 = MEM[R2 + 0]
// R1 will be 123
LDH – Load data from upper half-word of the 32-bit memory
- Syntax
LDH Rdst, Rsrc, offset
- Operands
Rdst – Register R[0..3], destination
Rsrc – Register R[0..3], holds address of destination, in 32-bit words
Offset – 13-bit signed value, offset in bytes
- Cycles
4 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction loads the upper 16-bit half-word from memory with address [Rsrc + offset / 4] into the destination register Rdst:
Rdst[15:0] = Mem[Rsrc + offset / 4][15:0]
Note
Note that the offset specified in bytes is converted to a 32-bit word offset before execution. See the section Note about addressing for more details.
Examples:
1: LDH R1, R2, 0x12 // R1 = MEM[R2 + 0x12 / 4]
2: .data // Data section definition
Addr1: .word 0x12345678 // Define label Addr1 16 bit
.set offs, 0x00 // Define constant offs
.text // Text section definition
MOVE R1, 1 // R1 = 1
MOVE R2, Addr1 // R2 = Addr1 / 4 (address of label is converted into words)
LDH R1, R2, offs // R1 = MEM[R2 + 0]
// R1 will be 0x1234
JUMP – Jump to an absolute address
- Syntax
JUMP Rdst
JUMP ImmAddr
JUMP Rdst, Condition
JUMP ImmAddr, Condition
- Operands
Rdst – Register R[0..3] containing address to jump to (expressed in 32-bit words)
ImmAddr – 13 bits address (expressed in bytes), aligned to 4 bytes
- Condition:
EQ – jump if last ALU operation result was zero
OV – jump if last ALU has set overflow flag
- Cycles
2 cycles to execute, 2 cycles to fetch next instruction
- Description
The instruction makes jump to the specified address. Jump can be either unconditional or based on an ALU flag.
Examples:
1: JUMP R1 // Jump to address in R1 (address in R1 is in 32-bit words)
2: JUMP 0x120, EQ // Jump to address 0x120 (in bytes) if ALU result is zero
3: JUMP label // Jump to label
...
label: nop // Definition of label
4: .global label // Declaration of global label
MOVE R1, label // R1 = label (value loaded into R1 is in words)
JUMP R1 // Jump to label
...
label: nop // Definition of label
JUMPR – Jump to a relative offset (condition based on R0)
- Syntax
JUMPR Step, Threshold, Condition
- Operands
Step – relative shift from current position, in bytes
Threshold – threshold value for branch condition
- Condition:
EQ (equal) – jump if value in R0 == threshold
LT (less than) – jump if value in R0 < threshold
LE (less or equal) – jump if value in R0 <= threshold
GT (greater than) – jump if value in R0 > threshold
GE (greater or equal) – jump if value in R0 >= threshold
Cycles
Conditions EQ, GT and LT: 2 cycles to execute, 2 cycles to fetch next instruction
Conditions LE and GE are implemented in the assembler using two JUMPR instructions:
// JUMPR target, threshold, LE is implemented as:
JUMPR target, threshold, EQ
JUMPR target, threshold, LT
// JUMPR target, threshold, GE is implemented as:
JUMPR target, threshold, EQ
JUMPR target, threshold, GT
Therefore the execution time will depend on the branches taken: either 2 cycles to execute + 2 cycles to fetch, or 4 cycles to execute + 4 cycles to fetch.
- Description
The instruction makes a jump to a relative address if condition is true. Condition is the result of comparison of R0 register value and the threshold value.
Examples:
1:pos: JUMPR 16, 20, GE // Jump to address (position + 16 bytes) if value in R0 >= 20
2: // Down counting loop using R0 register
MOVE R0, 16 // load 16 into R0
label: SUB R0, R0, 1 // R0--
NOP // do something
JUMPR label, 1, GE // jump to label if R0 >= 1
JUMPS – Jump to a relative address (condition based on stage count)
- Syntax
JUMPS Step, Threshold, Condition
- Operands
Step – relative shift from current position, in bytes
Threshold – threshold value for branch condition
- Condition:
EQ (equal) – jump if value in stage_cnt == threshold
LT (less than) – jump if value in stage_cnt < threshold
LE (less or equal) - jump if value in stage_cnt <= threshold
GT (greater than) – jump if value in stage_cnt > threshold
GE (greater or equal) — jump if value in stage_cnt >= threshold
Cycles
2 cycles to execute, 2 cycles to fetch next instruction
- Description
The instruction makes a jump to a relative address if condition is true. Condition is the result of comparison of count register value and threshold value.
Examples:
1:pos: JUMPS 16, 20, EQ // Jump to (position + 16 bytes) if stage_cnt == 20
2: // Up counting loop using stage count register
STAGE_RST // set stage_cnt to 0
label: STAGE_INC 1 // stage_cnt++
NOP // do something
JUMPS label, 16, LT // jump to label if stage_cnt < 16
STAGE_RST – Reset stage count register
- Syntax
STAGE_RST
- Operands
No operands
- Description
The instruction sets the stage count register to 0
- Cycles
2 cycles to execute, 4 cycles to fetch next instruction
Examples:
1: STAGE_RST // Reset stage count register
STAGE_INC – Increment stage count register
- Syntax
STAGE_INC Value
- Operands
Value – 8 bits value
- Cycles
2 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction increments the stage count register by the given value.
Examples:
1: STAGE_INC 10 // stage_cnt += 10
2: // Up counting loop example:
STAGE_RST // set stage_cnt to 0
label: STAGE_INC 1 // stage_cnt++
NOP // do something
JUMPS label, 16, LT // jump to label if stage_cnt < 16
STAGE_DEC – Decrement stage count register
- Syntax
STAGE_DEC Value
- Operands
Value – 8 bits value
- Cycles
2 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction decrements the stage count register by the given value.
Examples:
1: STAGE_DEC 10 // stage_cnt -= 10;
2: // Down counting loop example
STAGE_RST // set stage_cnt to 0
STAGE_INC 16 // increment stage_cnt to 16
label: STAGE_DEC 1 // stage_cnt--;
NOP // do something
JUMPS label, 0, GT // jump to label if stage_cnt > 0
HALT – End the program
- Syntax
HALT
- Operands
No operands
- Cycles
2 cycles to execute
- Description
The instruction halts the ULP coprocessor and restarts the ULP wakeup timer, if it is enabled.
Examples:
1: HALT // Halt the coprocessor
WAKE – Wake up the chip
- Syntax
WAKE
- Operands
No operands
- Cycles
2 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction sends an interrupt from the ULP coprocessor to the RTC controller.
If the SoC is in deep sleep mode, and ULP wakeup is enabled, this causes the SoC to wake up.
If the SoC is not in deep sleep mode, and ULP interrupt bit (RTC_CNTL_ULP_CP_INT_ENA) is set in RTC_CNTL_INT_ENA_REG register, RTC interrupt will be triggered.
Note
Note that before using WAKE instruction, ULP program may need to wait until RTC controller is ready to wake up the main CPU. This is indicated using RTC_CNTL_RDY_FOR_WAKEUP bit of RTC_CNTL_LOW_POWER_ST_REG register. If WAKE instruction is executed while RTC_CNTL_RDY_FOR_WAKEUP is zero, it has no effect (wake up does not occur). If the WAKE instruction is intended to be used while the main CPU is not in sleep mode then the RTC_CNTL_MAIN_STATE_IN_IDLE (bit 27) of RTC_CNTL_LOW_POWER_ST_REG can be used to check whether main CPU is in normal mode or sleep mode.
Examples:
1: is_rdy_for_wakeup: // Read RTC_CNTL_RDY_FOR_WAKEUP bit
READ_RTC_FIELD(RTC_CNTL_LOW_POWER_ST_REG, RTC_CNTL_RDY_FOR_WAKEUP)
AND r0, r0, 1
JUMP is_rdy_for_wakeup, eq // Retry until the bit is set
WAKE // Trigger wake up
REG_WR 0x006, 24, 24, 0 // Stop ULP timer (clear RTC_CNTL_ULP_CP_SLP_TIMER_EN)
HALT // Stop the ULP program
// After these instructions, SoC will wake up,
// and ULP will not run again until started by the main program.
1: check_wakeup: // Read RTC_CNTL_RDY_FOR_WAKEUP and RTC_CNTL_MAIN_STATE_IN_IDLE bit
READ_RTC_REG(RTC_CNTL_LOW_POWER_ST_REG, 27, 1)
MOVE r1, r0 // Copy result in to r1
READ_RTC_FIELD(RTC_CNTL_LOW_POWER_ST_REG, RTC_CNTL_RDY_FOR_WAKEUP)
OR r0, r0, r1
JUMP check_wakeup, eq // Retry until either of the bit are set
WAKE // Trigger wake up
HALT // Stop the ULP program
WAIT – wait some number of cycles
- Syntax
WAIT Cycles
- Operands
Cycles – number of cycles for wait
- Cycles
2 + Cycles cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction delays for given number of cycles.
Examples:
1: WAIT 10 // Do nothing for 10 cycles
2: .set wait_cnt, 10 // Set a constant
WAIT wait_cnt // wait for 10 cycles
TSENS – do measurement with temperature sensor
- Syntax
TSENS Rdst, Wait_Delay
- Operands
Rdst – Destination Register R[0..3], result will be stored to this register
Wait_Delay – number of cycles used to perform the measurement
- Cycles
2 + Wait_Delay + 3 * TSENS_CLK to execute, 4 cycles to fetch next instruction
- Description
The instruction performs measurement using TSENS and stores the result into a general purpose register.
Examples:
1: TSENS R1, 1000 // Measure temperature sensor for 1000 cycles,
// and store result to R1
ADC – do measurement with ADC
- Syntax
ADC Rdst, Sar_sel, Mux
ADC Rdst, Sar_sel, Mux, 0 — deprecated form
- Operands
Rdst – Destination Register R[0..3], result will be stored to this register
Sar_sel – Select ADC: 0 = SARADC1, 1 = SARADC2
Mux - selected PAD, SARADC Pad[Mux-1] is enabled. If the user passes Mux value 1, then ADC pad 0 gets used.
- Cycles
23 + max(1, SAR_AMP_WAIT1) + max(1, SAR_AMP_WAIT2) + max(1, SAR_AMP_WAIT3) + SARx_SAMPLE_CYCLE + SARx_SAMPLE_BITcycles to execute, 4 cycles to fetch next instruction- Description
The instruction makes measurements from ADC.
Examples:
.. only:: esp32
1: ADC R1, 0, 1 // Measure value using ADC1 channel 0 and store result into R1
1: ADC R1, 0, 1 // Measure value using ADC1 pad 2 and store result into R1
REG_RD – read from peripheral register
- Syntax
REG_RD Addr, High, Low
- Operands
Addr – Register address, in 32-bit words
High – Register end bit number
Low – Register start bit number
- Cycles
4 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction reads up to 16 bits from a peripheral register into a general purpose register:
R0 = REG[Addr][High:Low].
This instruction can access registers in RTC_CNTL, RTC_IO, SENS, and RTC_I2C peripherals. Address of the register, as seen from the ULP, can be calculated from the address of the same register on the PeriBUS1 as follows:
addr_ulp = (addr_peribus1 - DR_REG_RTCCNTL_BASE) / 4
Examples:
1: REG_RD 0x120, 7, 4 // load 4 bits: R0 = {12'b0, REG[0x120][7:4]}
REG_WR – write to peripheral register
- Syntax
REG_WR Addr, High, Low, Data
- Operands
Addr – Register address, in 32-bit words.
High – Register end bit number
Low – Register start bit number
Data – Value to write, 8 bits
- Cycles
8 cycles to execute, 4 cycles to fetch next instruction
- Description
The instruction writes up to 8 bits from an immediate data value into a peripheral register:
REG[Addr][High:Low] = data.
This instruction can access registers in RTC_CNTL, RTC_IO, SENS, and RTC_I2C peripherals. Address of the register, as seen from the ULP, can be calculated from the address of the same register on the PeriBUS1 as follows:
addr_ulp = (addr_peribus1 - DR_REG_RTCCNTL_BASE) / 4
Examples:
1: REG_WR 0x120, 7, 0, 0x10 // set 8 bits: REG[0x120][7:0] = 0x10
Convenience macros for peripheral registers access
ULP source files are passed through C preprocessor before the assembler. This allows certain macros to be used to facilitate access to peripheral registers.
Some existing macros are defined in soc/soc_ulp.h header file. These macros allow access to the fields of peripheral registers by their names.
Peripheral registers names which can be used with these macros are the ones defined in soc/rtc_cntl_reg.h, soc/rtc_io_reg.h, soc/sens_reg.h, and soc/rtc_i2c_reg.h.
- READ_RTC_REG(rtc_reg, low_bit, bit_width)
Read up to 16 bits from rtc_reg[low_bit + bit_width - 1 : low_bit] into R0. For example:
#include "soc/soc_ulp.h" #include "soc/rtc_cntl_reg.h" /* Read 16 lower bits of RTC_CNTL_TIME0_REG into R0 */ READ_RTC_REG(RTC_CNTL_TIME0_REG, 0, 16)
- READ_RTC_FIELD(rtc_reg, field)
Read from a field in rtc_reg into R0, up to 16 bits. For example:
#include "soc/soc_ulp.h" #include "soc/sens_reg.h" /* Read 8-bit SENS_TSENS_OUT field of SENS_SAR_SLAVE_ADDR3_REG into R0 */ READ_RTC_FIELD(SENS_SAR_SLAVE_ADDR3_REG, SENS_TSENS_OUT)
- WRITE_RTC_REG(rtc_reg, low_bit, bit_width, value)
Write immediate value into rtc_reg[low_bit + bit_width - 1 : low_bit], bit_width <= 8. For example:
#include "soc/soc_ulp.h" #include "soc/rtc_io_reg.h" /* Set BIT(2) of RTC_GPIO_OUT_DATA_W1TS field in RTC_GPIO_OUT_W1TS_REG */ WRITE_RTC_REG(RTC_GPIO_OUT_W1TS_REG, RTC_GPIO_OUT_DATA_W1TS_S + 2, 1, 1)
- WRITE_RTC_FIELD(rtc_reg, field, value)
Write immediate value into a field in rtc_reg, up to 8 bits. For example:
#include "soc/soc_ulp.h" #include "soc/rtc_cntl_reg.h" /* Set RTC_CNTL_ULP_CP_SLP_TIMER_EN field of RTC_CNTL_STATE0_REG to 0 */ WRITE_RTC_FIELD(RTC_CNTL_STATE0_REG, RTC_CNTL_ULP_CP_SLP_TIMER_EN, 0)