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I've been working on a homemade Z80 computer, and it's time to load some sort of program into it to see if it's working.
Since I don't have an EEPROM programmer, I decided to make a simple PIC program to load a program onto the EEPROM I'm going to be using with the Z80.
I don't think it's working.
If I hook up leds to the address output, I can see the address incrementing. I can also see the write enable going low and high for each byte as I should. But when I hook up leds to the data output, they are always off.
Here's my source code, can you guys spot anything wrong with it?
Also, I suspect it might be a hardware fail (do I need pull up/down resistors of any kind when connecting the PIC to the EEPROM?)
Sorry if the indentation looks weird, Notepad adjusts tab widths to make it look nice but I don't think it's going to do that here.
Thanks a lot.
Since I don't have an EEPROM programmer, I decided to make a simple PIC program to load a program onto the EEPROM I'm going to be using with the Z80.
I don't think it's working.
If I hook up leds to the address output, I can see the address incrementing. I can also see the write enable going low and high for each byte as I should. But when I hook up leds to the data output, they are always off.
Here's my source code, can you guys spot anything wrong with it?
Also, I suspect it might be a hardware fail (do I need pull up/down resistors of any kind when connecting the PIC to the EEPROM?)
Sorry if the indentation looks weird, Notepad adjusts tab widths to make it look nice but I don't think it's going to do that here.
Thanks a lot.
Rich (BB code):
LIST P=16F628A, R=DEC
#include "P16F628A.INC"
__config _INTRC_OSC_NOCLKOUT & _LVP_OFF & _WDT_OFF & _PWRTE_ON & _BODEN_ON
CBLOCK 0x20
d1
d2
eep_byte
address
read_back
ENDC
ORG 0x000
movlw 7
movwf CMCON ; CMCON=7 set comperators off
; initialize ports __ __
movlw b'10010000' ; OE and WE high (disabled)
movwf PORTA
clrf address
clrf eep_byte
clrf PORTB
bsf STATUS,RP0 ; bank 1
bsf OPTION,7 ; disable PORTB pull ups
clrf TRISA
clrf TRISB
bcf STATUS,RP0 ; bank 0
loop call read_ee ; read byte from pic eeprom
movwf eep_byte
movf address,W ; give address to eprom
movwf PORTA
movf eep_byte,W ; give data to eprom
movwf PORTB
bcf PORTA,4 ; eeprom write enable
call delay ; wait a little
bsf PORTA,4 ; eeprom write disable
call delay ; generous delays
bsf STATUS,RP0 ; bank1
movlw b'11111111'
movwf TRISB ; set portB to inputs
bcf STATUS,RP0 ; bank0
bcf PORTA,7 ; eeprom output enable
call delay
movf PORTB,W
movwf read_back ; read back data from eprom
call delay
bsf PORTA,7 ; eeprom output disable
incf address,F ; increase address in eprom
goto loop
read_ee bsf STATUS,RP0 ; Read byte from eeprom
movf address,W
movwf EEADR
bsf EECON1,RD
movf EEDATA,W ; Store result in w
bcf STATUS,RP0
return
delay movlw 0x1E
movwf d1
movlw 0x4F
movwf d2
delay_0 decfsz d1, f
goto $+2
decfsz d2, f
goto delay_0
goto $+1
nop
return
org 2100h
de "Hello"
END
