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;
; $Id: test_eeprom.asm,v 1.1 2001/10/16 02:43:37 troth Exp $
;
;;; Test writing to and reading from the eeprom memory space.
.include "8515def.inc"
rjmp MAIN ; reset
nop ; int0
nop ; int1
nop ; timer1 capt
nop ; timer1 compa
nop ; timer1 compb
nop ; timer1 ovf
nop ; timer0 ovf
nop ; spi, stc
nop ; uart, rx
nop ; uart, udre
nop ; uart, tx
nop ; ana_comp
MAIN:
;; init stack pointer to 0x025f (the last byte of int sram)
ldi r16, lo8(RAMEND); low byte of end of int sram
out SPL, r16
ldi r16, hi8(RAMEND); high byte of end of int sram
out SPH, r16
;; write a byte to eeprom
ldi r16, 0x00 ; set up low addr
ldi r17, 0x00 ; set up high addr
ldi r18, 0x55 ; set up the data
rcall SUB_EE_WR ; call subroutine to write data
ldi r18, 0x00 ; clear r18, so we'll know if we read back correctly
;; read a byte from eeprom
rcall SUB_EE_RD
mov r0, r18 ; move result from r18 to r0
;; jmp to done
rjmp DONE
;;; Subroutine for writing a byte to eeprom
;;; r16 -> EEARL
;;; r17 -> EEARH
;;; r18 -> data to be written
SUB_EE_WR:
sbic EECR, EEWE ; poll the EEWE bit to see if we can write
rjmp SUB_EE_WR ; if EEWE is cleared, skip the rjmp
out EEARL, r16 ; write low addr to EEARL
out EEARH, r17 ; write high addr to EEARH
out EEDR, r18 ; write data to EEDR
sbi EECR, EEMWE ; write 1 to EEMWE
sbi EECR, EEWE ; write 1 to EEWE
WR_POLL:
sbic EECR, EEWE ; poll the EEWE bit until write has completed
rjmp WR_POLL ; rjmp is skipped once EEWE is cleared
ret ; return from subroutine
;;; Subroutine for reading a byte from eeprom
;;; r16 -> EEARL
;;; r17 -> EEARH
;;; result is placed in r18
SUB_EE_RD:
sbic EECR, EEWE ; poll the EEWE bit to see if we can write
rjmp SUB_EE_WR ; if EEWE is cleared, skip the rjmp
out EEARL, r16 ; write low addr to EEARL
out EEARH, r17 ; write high addr to EEARH
sbi EECR, EERE ; strobe the eeprom
in r18, EEDR ; move data read from eedr to r18
ret
DONE: nop
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