TITLE        "R/W EEPROM"
LIST  P = 16C54
;Serial Eprom interface to PIC16C5X.
;REV 2.0        8/26/92.
;
;Define Equates:
;       
 PIC54   EQU     1FFH
;
PAGE
;
 ORG     0
START
 goto    main            ;run test program
;
PAGE
;
TRUE    EQU     1
FALSE   EQU     0
S93C46  EQU     FALSE
S93LC46 EQU     FALSE
S93C56  EQU     FALSE
S93LC56 EQU     FALSE
S93C66  EQU     TRUE
S93LC66 EQU     FALSE
wire3   equ     TRUE
org8    EQU     FALSE
;
IF      S93LC46
 IF      org8
 LC468   EQU     TRUE
 XC46    EQU     FALSE
 H16     EQU     FALSE
 H8      EQU     FALSE
 ELSE
 LC468   EQU     FALSE
 XC46    EQU     TRUE
 H16     EQU     FALSE
 H8      EQU     FALSE
 ENDIF
ELSE
ENDIF
IF      S93C46
 LC468   EQU     FALSE
 XC46    EQU     TRUE
 H16     EQU     FALSE
 H8      EQU     FALSE
ENDIF
IF      S93C56 + S93C66 + S93LC56 + S93LC66
 IF      org8
 H8      EQU     TRUE
 H16     EQU     FALSE
 LC468   EQU     FALSE
 XC46    EQU     FALSE
 ELSE
 H16     EQU     TRUE
 H8      EQU     FALSE
 LC468   EQU     FALSE
 XC46    EQU     FALSE
 ENDIF
ELSE
ENDIF

;********************************************************************
;*                      Register Assignments                        *
;********************************************************************

indir   equ     0       ;Use this register as source/desTInaTIon
   ;for indirect addressing.
pc      equ     2       ;PIC Program Counter.
status  equ     3       ;PIC Status Register.
fsr     equ     4       ;File Select Register.
serial  equ     5       ;Port used for 93CX6 control. 
   ;The following four registers must be
   ;located consecuTIvely in memory.
cmd     equ     1a      ;This register contains the 4 bit
   ;command op code for 93CX6 as follows:
   ;bit 7 msb of command op code
   ;bit 6 next bit of op code
   ;bit 5 next bit of op code
   ;bit 4 lsb of op code
   ;bit 3 A8 of address in case of
   ;56/66 in 8 bit mode.
addr    equ     1b      ;memory address of lower 7/8 bits
highb   equ     1c      ;Used in read/write routines to store the
   ;upper byte of a 16 bit data word,
   ;or the data in a 8 bit data word
lowb    equ     1d      ;Used in read/write routines to store the
   ;lower byte of a 16 bit data word,
   ;or not used in 8 bit data word.

cnthi   equ     1e      ;Used as the upper byte of a sixteen bit
   ;loop counter in RDYCHK routine.
cnt     equ     1f      ;Used as the lower byte of a sixteen bit 
   ;loop counter in RDYCHK routine, and 
   ;elswhere as an eight bit counter.
temp_cmd equ    1e      ;doubles as a temp register for cmd        
temp_addr equ   1f      ;doubles as a temp register for addr

;********************************************************************
;*                      Bit Assignments                             *
;********************************************************************

carry   equ     0               ;Carry Flag of Status Register.
zflag   equ     2               ;Zero Flag of Status Register.

cs      equ     2               ;Port pin tied to CS on 93CX6.
din     equ     1               ;Port pin tied to DI on 93CX6.
dout    equ     1               ;Port pin tied to DO on 93CX6.
clock   equ     3               ;Port pin tied to CLK on 93CX6.

;********************************************************************
;*                      General Assignments                         *
;********************************************************************

no_err  equ     0               
error   equ     1               
tries   equ     20      ;After issuing a WRITE, ERASE, ERAL, or WRAL
   ;command, the approximate number of machine
   ;cycles X 256 to wait for the RDY status.
   ;This value must be adjusted for operating
   ;frequencies other than 4 MHz.

read    equ     b'10000000'     ;read command op code
write   equ     b'01000000'     ;write command op code
erase   equ     b'11000000'     ;erase command op code
ewen    equ     b'00110000'     ;erase enable command op code
ewds    equ     b'00000000'     ;erase disable command op code
eral    equ     b'00100000'     ;erase all command op code
wral    equ     b'00010000'     ;write all command op code

;********************************************************************
;*                      Macro Definitions                           *
;********************************************************************

sel     MACRO                   ;Selects the 93CX6 device.
 bsf     serial,cs       ;Chip Select (CS) = '1' to select
 ENDM                    ;the device               

dsel    MACRO                   ;De-select the 93CX6 device.
 bcf     serial,cs       ;Chip Select (CS) = '0' to de-select
    ;the device.
 ENDM

strtbt MACRO ;Issue the Start Bit to the 93CX6.