Operations:

Syntax:

Operation:

Operands:

Program Counter:

Opcode

Comment

Stack

SPM

PS(RAMPZ:Z) = 0xffff

None

PC = PC + 1

1001010111101000

Erase program memory page

SPM

PS(RAMPZ:Z) = R1:R0

None

PC = PC + 1

1001010111101000

Write program memory word

SPM

PS(RAMPZ:Z) = R1:R0

None

PC = PC + 1

1001010111101000

Load page buffer

SPM

PS(RAMPZ:Z) = BUFFER

None

PC = PC + 1

1001010111101000

Write page buffer to program memory

SPM

BLBITS = R1:R0

None

PC = PC + 1

1001010111101000

Set Boot Loader Lock bits

Description

SPM can be used to erase a page in the program memory, to write a page in the program memory (that is already erased), and to set Boot Loader Lock bits. In some devices, the Program memory can be written one word at a time. In other devices, an entire page can be programmed simultaneously after first filling a temporary page buffer. In all cases, the program memory must be erased one page at a time. When erasing the program memory, the RAMPZ and Z-register are used as page address. When writing the program memory, the RAMPZ and Z-register are used as page or word address, and the R1:R0 register pair is used as data(1). The Flash is word-accessed for code space write operations, so the least significant bit of the RAMPZ register concatenated with the Z register should

be set to ‘0'. When setting the Boot Loader Lock bits, the R1:R0 register pair is used as data. Refer to the device documentation for the detailed description of SPM usage. This instruction can address the entire program memory.

The SPM instruction is not available on all devices. Refer to Appendix A.

Note: 1. R1 determines the instruction high byte, and R0 determines the instruction low byte.

Status Register (SREG) and Boolean Formula

I

–

T

–

H

–

S

–

V

–

N

–

Z

–

C

–

Example: 

 ; This example shows SPM write of one page for devices with page write
 ; - the routine writes one page of data from RAM to Flash
 ;   the first data location in RAM is pointed to by the Y-pointer
 ;   the first data location in Flash is pointed to by the Z-pointer
 ; - error handling is not included
 ; - the routine must be placed inside the boot space
 ;   (at least the do_spm sub routine)
 ; - registers used: r0, r1, temp1, temp2, looplo, loophi, spmcrval
 ; (temp1, temp2, looplo, loophi, spmcrval must be defined by the user)
 ; storing and restoring of registers is not included in the routine
 ; register usage can be optimized at the expense of code size
         equ   PAGESIZEB = PAGESIZE*2       ; PAGESIZEB is page size in BYTES, not words
        org   SMALLBOOTSTART
 write_page:
                                           ; page erase
        ldi   spmcrval, (1<<PGERS) + (1<<SPMEN)
        call  do_spm
                                           ; transfer data from RAM to Flash page buffer
        ldi   looplo, low(PAGESIZEB)       ; init loop variable
        ldi   loophi, high(PAGESIZEB)      ; not required for PAGESIZEB<=256
 wrloop: 
        ld    r0, Y+
        ld    r1, Y+
        ldi   spmcrval, (1<<SPMEN)
        call  do_spm
        adiw  ZL, 2
        sbiw  looplo, 2                    ; use subi for PAGESIZEB<=256
        brne  wrloop
                                           ; execute page write
        subi  ZL, low(PAGESIZEB)           ; restore pointer
        sbci  ZH, high(PAGESIZEB)          ; not required for PAGESIZEB<=256
        ldi   spmcrval, (1<<PGWRT) + (1<<SPMEN)
        call  do_spm
                                            ; read back and check, optional
        ldi   looplo, low(PAGESIZEB)       ; init loop variable
        ldi   loophi, high(PAGESIZEB)      ; not required for PAGESIZEB<=256
        subi  YL, low(PAGESIZEB)           ; restore pointer
        sbci  YH, high(PAGESIZEB)
 rdloop: 
        lpm   r0, Z+
        ld    r1, Y+
        cpse  r0, r1
        jmp   error
        sbiw  looplo, 2                    ; use subi for PAGESIZEB<=256
        brne  rdloop
         ret                                ; return
do_spm:
        in    temp2, SREG                  ; input: spmcrval determines SPM action
        cli                                ; disable interrupts if enabled, store status
 wait:
        in    temp1, SPMCR                 ; check for previous SPM complete
        sbrc  temp1, SPMEN
        rjmp  wait
         out   SPMCR, spmcrval              ; SPM timed sequence
        spm
         out   SREG, temp2                  ; restore SREG (to enable interrupts if 
                                           ; originally enabled)
        ret

Words

1 (2 bytes)

Table Cycles

Name

Cycles

AVRe

-(1)

AVRxm

N/A

AVRxt

N/A

AVRrc

N/A

Note:

1.

Varies with the programming time of the device.