; ee.asm
LIST P=16C74A, F=INHX8M
__CONFIG _BODEN_OFF & _CP_OFF & _WDT_OFF & _XT_OSC
include <p16c74a.inc>
;*****************************************************************************
; This application written by Virgil Stamps, 6-12-99
; I had an application that needed configuration files for various modes of operation.
; A 24C32 I2C EEPROM provides 4Kx8 non-volatile storage. A PIC 16C74 is the processor.
; "Creating electronic products for fun and profit." This code is given
; to the public domain. If you need help, email author at stamps@brokersys.com
;*****************************************************************************
RESET_V EQU 0x0000 ; Address of RESET Vector
ISR_V EQU 0x0004 ; Address of Interrupt Vector
ORG RESET_V ; RESET vector location
RESET GOTO START
ORG ISR_V ; Interrupt vector location
nop ; interrupt service would be here
retfie
INIT bsf STATUS,RP0 ; bank 1
movlw b'10010110'
movwf TRISC ; rc7= RX rc6= TX rc5=SDO rc4=SDI rc3=SCLK rc1=na rc0=na
BCF STATUS, RP0 ; bank 0
clrf event
return
;*****************************************************************************
; Program start. Simple poll loop. A good place for breakpoint and testing.
;*****************************************************************************
START CALL INIT ; Initialize Processor Registers
bsf event,ee_busy ; read block
movlw .0 ; which block
movwf BLK
POLL nop
btfsc event,ee_busy ; ee busy?
call EE_SERVICE ; service eeprom if needed
GOTO POLL
; Driver for Microchip 24C32A Serial EEPROM (32K-bit).
; Generic program listing for those seeking information on programming this type EEPROM.
; Approximately 30 ms to read and 80 ms to write a block of 80 bytes.
; The EEPROM is organized as virtual memory accessed by a block number
; and temporarily stored in RAM at BLOCK (0x0A0 - 0x0EF)
; A 32K-bit device has a maximum of 51 blocks. 4,096 bytes / 80 = 51.2 blocks
; A virtual memory location in your application could be defined as BLK (0-50)
; and a offset (0-79).
EE equ PORTC ; EEPROM port
SDA equ 1 ; EE data
SCL equ 0 ; EE clk
block equ 0x0A0
blk_size equ 0x050 ; 80 decimal
; VARIABLES defined in low RAM Arbitrary as to where you want to put them
event equ 0x03D ; event register where:
ee_busy EQU 2 ; service requested 1=busy, 0=idle
ee_write EQU 1 ; 1=write, 0=read
ee_blk_op EQU 0 ; 1=read or write block operation, 0=idle
ADDR0 equ 0x03E ; address high byte
ADDR1 equ 0x03F ; address low byte
BLK equ 0x040 ; block number (0-50)
BLKC equ 0x041 ; block counter
blkptr equ 0x042 ; block pointer
o_data equ 0x043 ; output data
i_data equ 0x044 ; input data
ee_cntr4 equ 0x045 ; temp counter
ee_cntr3 equ 0x046 ; temp counter
ee_cntr2 equ 0x047 ; temp counter
ee_cntr1 equ 0x048 ; temp counter
X_DELAY equ 0x04B ; delay counter MS
DELAY equ 0x04C ; delay counter LS
;*****************************************************************************
; This application burst mode writes 10 groups of 8-bytes each.
; The read function block reads 80-bytes in a loop.
; To write the 80 bytes at block, set BLK= block number in EEPROM, set event,ee_busy,
; set event,ee_write, call EE_SERVICE.
; To read 80 bytes to block from EEPROM, set BLK= block number in EEPROM,
; set event,ee_busy, clear event,ee_write, call EE_SERVICE.
; on return: event,ee_busy is zero, event,ee_block is zero.
;*****************************************************************************
EE_SERVICE btfss event,ee_busy ; busy?
return ; no
call EEPRMSVC ; service eeprom
btfss event,ee_busy
goto EE_SERVICE
movlw .10
call X_DELAY500
goto EE_SERVICE ; if yes
EEPRMSVC btfsc event,ee_write ; write to ee?
goto write_block ; if yes
goto read_block ; no, read a block
write_block btfsc event,ee_blk_op ; writing a block now?
goto write_busy ; if yes
bsf event,ee_blk_op ; no, signal writing a block
call set_addr
movlw block
movwf blkptr ; addr of block buffer
movlw .10
movwf ee_cntr4 ; write 10 groups of 8 bytes each
write_busy call low_scl
call low_sda
movlw blk_size/.10
movwf ee_cntr2
movf blkptr,w
movwf FSR
call w_block
decfsz ee_cntr4 ; done all groups of 8?
goto poll_ack ; if no
bcf event,ee_blk_op ; eeprom block operation done
bcf event,ee_write ; eeprom not writing
bcf event,ee_busy ; eeprom not busy
goto delay50ms ; return after delay
poll_ack movlw .100
movwf ee_cntr3
ack_loop decfsz ee_cntr3
goto ack_tst
goto err
ack_tst call strt
movlw 0x0a0
call out_byte
call wait
btfsc PORTC,SDA ; did chip acknowledge?
goto clkit ; if no
goto pulse ; yes, so exit
clkit call pulse
goto ack_loop ; poll again
err nop ; EEPROM is bad (add your own error recovery)
goto err ; eeprom did not respond in 100 tries
w_block call strt ; burst write 8 bytes
movlw 0x0a0
call out_byte
call ack
movf ADDR0,w ; ms addr
call out_byte
call ack
movf ADDR1,w ; ls addr
call out_byte
call ack
wrtblk movf INDF,w ; byte to write
call out_byte
call ack
incf FSR
incf blkptr
movlw .1
addwf ADDR1 ; EEPROM addr low
btfsc STATUS,C
incf ADDR0 ; EEPROM addr high
decfsz ee_cntr2
goto wrtblk
call stop
return
read_block bsf event,ee_blk_op ; signal reading a block
call set_addr
call low_scl
call high_sda
call high_scl ; idle bus
movlw block
movwf FSR ; addr of block buffer
movlw blk_size
movwf ee_cntr2 ; bytes to copy
call strt
movlw 0x0a0 ; write preface
call out_byte
call ack
movf ADDR0,w ; ms address
call out_byte
call ack
movf ADDR1,w ; ls address
call out_byte
call ack
call strt
movlw 0x0a1
call out_byte ; read preface
more_seq call ack
call in_byte ; fetch the byte
movf i_data,w
movwf INDF ; copied to current block
incf FSR ; point to next address in block
movlw .1
addwf ADDR1
btfsc STATUS,C
incf ADDR0
decfsz ee_cntr2 ; read all bytes?
goto more_seq
call stop
bcf event,ee_blk_op ; block read is done
bcf event,ee_busy ; ee not busy
return
out_byte movwf o_data ; output 8 bits to eeprom
movlw .8
movwf ee_cntr1
o_loop rlf o_data ; msb to carry
call low_sda
btfsc STATUS,C ; is it a 1?
call high_sda
call pulse
decfsz ee_cntr1 ; done?
goto o_loop ; no
call high_sda
return
in_byte movlw .8 ; input 8 bits from eeprom
movwf ee_cntr1
call high_sda
i_loop call high_scl ; data valid
bcf STATUS,C
btfsc PORTC,SDA
bsf STATUS,C
rlf i_data
call low_scl
call wait
decfsz ee_cntr1
goto i_loop
return
ack call high_sda ; acknowledge operation
btfsc PORTC,SDA ; bit low?
goto force0 ; if no
goto pulse ; slave acknowledges
force0 call low_sda ; master acknowledges
call pulse
goto high_sda ; return as input
strt call high_sda
call high_scl
call low_sda ; strt condition
goto low_scl
stop call low_sda
call high_scl
call high_sda ; stop condition
goto low_scl
low_sda call wait
BSF STATUS, RP0 ; bank 1
bcf TRISC,SDA ; output
bcf STATUS, RP0 ; bank 0
bcf PORTC,SDA
goto wait
high_sda call wait
BSF STATUS, RP0 ; bank 1
bsf TRISC,SDA ; input
bcf STATUS, RP0 ; bank 0
bsf PORTC,SDA
goto wait
low_scl bcf EE,SCL ; clock line goes low
return
high_scl bsf EE,SCL ; clock line goes high
return
wait nop ; delay for the chip
nop
nop
nop
return
pulse call high_scl ; one clock pulse
call wait
goto low_scl
; subroutine to compute block address: addr = n * 80
set_addr clrf ADDR0 ; assume 1st block
clrf ADDR1
movf BLK,w
movwf BLKC
movf BLK,w
btfss STATUS,Z ; zero?
goto next_addr2 ; if n
goto set_done ; if yes
next_addr2 bcf STATUS,C ; set ADDR0 and ADDR1 modulo 80
movlw blk_size ; sizeof block
addwf ADDR1,f
btfsc STATUS,C ; overflow?
incf ADDR0 ; if yes
decfsz BLKC
goto next_addr2 ; if no
set_done return
; a delay routine
delay50ms movlw .100
X_DELAY500 MOVWF X_DELAY ; +1 1 cycle
X_DELAY500_LOOP CALL DELAY500 ; step1 wait 500uSec
DECFSZ X_DELAY, F ; step2 1 cycle
GOTO X_DELAY500_LOOP ; step3 2 cycles
RETURN ; +2 2 cycles
DELAY500 MOVLW D'165' ; +1 1 cycle
MOVWF DELAY ; +2 1 cycle
DELAY500_LOOP DECFSZ DELAY, F ; step 1 1 cycle
GOTO DELAY500_LOOP ; step 2 2 cycles
RETURN ; +3 2 cycles
END ; End of program
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