PIC读写93C46程序

PIC读写93C46程序

;********************************************************************
;*                      PICALC Directives Section                   *
;********************************************************************

 SUBTITL "93C46 3 WIRE INTERFACE ROUTINE"
 LIST     P=16C54,N=40,C=132

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

indir   equ     0x00            ;Use this register as source/destination for
    ;indirect addressing.
pc      equ     0x02            ;PIC Program Counter.
status  equ     0x03            ;PIC Status Register.
fsr     equ     0x04            ;File Select Register.
serial  equ     0x05            ;Port used for 93C46 control.  Since Port A
    ;is 4 bits wide, we'll use all of Port A.

    ;The following three registers must be
    ;located consecutively in memory.
cmd     equ     0x10            ;This register contains the 2 bit 93C46
    ;command is the upper 2 bit positions and
    ;memory address in the lower 6.
highb   equ     0x11            ;Used in read/write routines to store the
    ;upper byte of a 16 bit 93C46 data word.
lowb    equ     0x12            ;Used in read/write routines to store the
    ;lower byte of a 16 bit 93C46 data word.

cnthi   equ     0x13            ;Used as the upper byte of a sixteen bit loop
    ;counter in RDYCHK routine.
cnt     equ     0x14            ;Used as the lower byte of a sixteen bit loop
    ;counter in RDYCHK routine, and elsewhere as
    ;an eight bit counter.

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

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

;For the 3 wire interface, connect the din and dout to the same
;i/o line of the PIC16C5X.
cs      equ     0               ;Port pin tied to CS on 93C46.
din     equ     1               ;Port pin tied to DI on 93C46.
dout    equ     1               ;Port pin tied to DO on 93C46.
clock   equ     2               ;Port pin tied to CLK on 93C46.

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

no_err  equ     0               ;
error   equ     1               ;
tries   equ     0x04            ;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     0x80            ;93C46 Read command.
write   equ     0x40            ;93C46 Write command.
erase   equ     0xC0            ;93C46 Erase command.
ewen    equ     0x30            ;93C46 Erase/Write Enable command.
ewds    equ     0x00            ;93C46 Erase/Write Disable command.
eral    equ     0x20            ;92CXX Erase All command.
wral    equ     0x10            ;92CXX Write All command.

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

sel     MACRO                   ;Selects the 93C46 device.
 bsf     serial,cs       ;Chip Select (CS) = '1' to select the device.
 ENDM

dsel    MACRO                   ;De-select the 93C46 device.
 bcf     serial,cs       ;Chip Select (CS) = '0' to de-select the
    ;device.
 ENDM

strtbt  MACRO                   ;Issue the Start Bit to the 93C46.
 bsf     serial,din      ;Start Bit = '1'.
 clkit                   ;Clock it out.
 ENDM

clkit   MACRO                   ;Clocks a serial data bit into or out of the
    ;93C46 device.
 bsf     serial,clock    ;Clock (CLK) = '1'.

 nop                     ;Adjust the number of nop instructions
    ;between the assertion and de-assertion of
    ;CLK in proportion to the PIC operating
    ;frequency.  Refer to the 93C46 data for the
    ;minimum CLK period.
   
 bcf     serial,clock    ;Clock (CLK) = '0'.
 ENDM

;********************************************************************
;*                      Power-On/Reset Entry Point                  *
;********************************************************************

reset_  org     0x1FF
 goto    main

;********************************************************************
;*                      93C46 Routines                              *
;********************************************************************
 org     0x000           ;Locate all subroutines in the lower half of
    ;a Program Memory Page.

;********************************************************************
;*                      DOUT8                                       *
;********************************************************************
    ;Dout8 will output 8 bits of data to the
    ;93C46.  Before calling this routine, the FSR
    ;must point to the byte being transmitted.

dout8   movlw   0x08            ;Initialize loop counter.
 movwf   cnt             ;

d_o_8   bcf     serial,din      ;Assume that the bit to be transfered is a
    ;'0'.  Hence, de-assert DI.
 rlf     indir           ;Rotate the actual bit to be transferred into
    ;the carry bit.
 btfsc   status,carry    ;Test the carry, if our assumption was
    ;correct, skip the next instruction.
 bsf     serial,din      ;No, actual bit was a '1'.  Assert DI.
 clkit                   ;Clock the 93C46.
 decfsz  cnt             ;Repeat until cnt = 0.
 goto    d_o_8           ;Cnt still > 0.
 rlf     indir           ;Restore register to its original condition.
 retlw   no_err          ;Exit with good status.

;********************************************************************
;*                      DIN8                                        *
;********************************************************************
    ;Din8 will input 8 bits of data from the
    ;93C46.  Before calling this routine, the FSR
    ;must point to the register being used to
    ;hold the incomming data.
din8    movlw   0x08            ;Initialize loop counter.
 movwf   cnt             ;
;for the 3 wire interface the direction of the i/o line connected to
;din and dout has to converted from an output to an input.
 movlw   b'00000010'     ;convert RA1 to an input
 tris    serial          ;       /

d_i_8   clkit                   ;Clock a bit out of the 93C46.
 rlf     indir           ;Make room for the incomming bit in the
    ;destination register.
 bcf     indir,0         ;Assume that the incomming bit is a '0' and
    ;clear the LSB of the destination register.
 btfsc   serial,dout     ;Test the incomming bit, if our assumption
    ;was correct, skip the next instruction.
 bsf     indir,0         ;No, actual bit is a '1'.  Set the LSB of the
    ;destination register.
 decfsz  cnt             ;Repeat until cnt = 0.
 goto    d_i_8           ;Cnt still > 0
;for a 3 wire interface, convert the RA1 line back to an output
 movlw   0               ;make RA1 to an output
 tris    serial          ;       /
 retlw   no_err          ;Exit with good status.

;********************************************************************
;*                      RDYCHK                                      *
;********************************************************************
    ;Rdychk will read the 93C46 READY/BUSY status
    ;and wait for RDY status within the alloted
    ;number of processor cycles.  If RDY status
    ;is not present after this set period, the
    ;routine will return with an error status.

rdychk  movlw   tries           ;Initialize time-out counter.
 movwf   cnthi           ;
 clrf    cnt             ;
;for a 3 wire interface, make the RA1 line an input
 movlw   b'00000010'     ;
 tris    serial
 dsel                    ;De-select the 93C46.

;       nop                     ;NOTE:  Check the 93C46 data sheet for
    ;minimum CS low time.  Depending upon
    ;processor frequency, a nop(s) may be
    ;between the assertion and de-assertion of
    ;Chip Select.

 sel                     ;Re-select the 93C46.
notrdy  btfsc   serial,dout     ;If DO is a '0', 93C46 has yet to completed
    ;the last operation (still busy).
 goto    no_error        ;Otherwise RDY status is present within the
    ;alloted time, and return with good status.
 decfsz  cnt             ;No, not yet ready.  Decrement the LSB of our
    ;16 bit timer and check for expiration.
 goto    notrdy          ;Still some time left.  Try again.
 decfsz  cnthi           ;Least significant byte expired - decrement
    ;and check for expiration of the MSB.
 goto    notrdy          ;Still some time left.  Try again.
;for a 3 wire interface, convert RA1 line back to an ouput
 movlw   0               ;convert RA1 to an output
 tris    serial          ;       /
 retlw   error           ;RDY status was not present in the alloted
    ;time, return with error status.
no_error
;for a 3 wire interface, convert RA1 line back to an ouput
 movlw   0               ;convert RA1 to an output
 tris    serial          ;       /
 retlw   no_err

;********************************************************************
;*                      SEE                                         *
;********************************************************************

    ;See will control the entire operation of a
    ;93C46 device.  Prior to calling the routine,
    ;load a valid command/memory address into
    ;location cmd, and for WRITE or WRAL
    ;commands, load registers highb and lowb with
    ;16 bits of write data.  Upon exit, the W
    ;register will contain the completion status.
    ;Only 93C46 instructions which require a
    ;status check can return with an error as the
    ;completion status.  The values that denote
    ;the completion status are defined as
    ;variables 'error' and 'no_err' in the
    ;general assignments section.

see     movlw   cmd             ;Load W with the location of the cmd
    ;register.
 movwf   fsr             ;Transfer that information into the File
    ;Select Register.  The fsr now points to
    ;location cmd.
 sel                     ;Select the 93C46.
 strtbt                  ;Send a start bit.
 call dout8              ;Transmit the 2 bit command and six bit
    ;address.
 btfsc   cmd,6           ;Check for a WRITE or ERASE command.
 goto    see2            ;Yes, parse the command further.
 btfsc   cmd,7           ;Check for a READ command.
 goto    read_           ;Yes, process READ command.
 btfsc   cmd,5           ;Check for a EWEN or ERAL command.
 goto    see3            ;Yes, parse the command further.
 btfsc   cmd,4           ;Check for a WRAL command.
 goto    write_          ;Yes, process WRITE/WRAL command.

exit_   dsel                    ;No further processing required; 93C46
    ;command completed.
 retlw   no_err          ;Return with good completion status.

see2    btfss   cmd,7           ;Check for a ERASE command.
 goto    write_          ;No, process WRITE command.
exit2_  call    rdychk          ;ERASE command requires a status check.
 dsel                    ;De-select the 93C46.
 addwf   pc              ;Compute completion status from results of
    ;status check.
 retlw   no_err          ;Return with good completion status.
 retlw   error           ;Return with bad completion status.

see3    btfsc   cmd,4           ;Check for a EWEN command.
 goto    exit_           ;Yes, no further processing required, exit
    ;now.
 goto    exit2_          ;No, ERAL command which requires a status
    ;check.

read_   incf    fsr             ;Increment the File Select Register to point
    ;to the register receiving the upper byte of
    ;the incomming 93C46 data word.
 call    din8            ;Input the upper byte.
 incf    fsr             ;Increment the File Select Register to point
    ;to the register receiving the lower byte.
 call    din8            ;Input 8 more bits.
 goto    exit_           ;No further processing required, exit now.

write_  incf    fsr             ;Increment the File Select Register to point
    ;to the upper byte of the 16 bit 93C46 data
    ;word to be transmitted.
 call    dout8           ;Output that byte.
 incf    fsr             ;Increment the File Select Register to point
    ;to the lower byte.
 call    dout8           ;Output the lower byte of the 16 bit 93C46
    ;data word.
 goto    exit2_          ;Exit with a status check.

;********************************************************************
;*                      Test Program                                *
;********************************************************************
 main                    ;We've include a sample program to exercise
    ;the PIC to 93C46 interface using a simple
    ;erase, write and varify routine.
 
 clrf    serial          ;Clear the port tied to the 93C46 device.
 movlw   b'11110100'     ;Intialize the data direction register for
 tris    serial          ;that port.
 
 movlw   ewen            ;Load W with the Erase/Write Enable command.
 movwf   cmd             ;Transfer W into cmd register.
 call    see             ;Enable the 93C46 device.

 movlw   eral            ;Load W with the Erase All command.
 movwf   cmd             ;Transfer W into cmd register.
 call    see             ;Erase the 93C46.
 xorlw   error           ;Check completion status.
 btfsc   status, ***lag   ;Test for error condition.
 goto    errloop         ;Yes, bad completion status, error-out.

    ;Write loop:
loopcnt equ     0x1F            ;Define an unused location for our test
    ;program loop counter.
tstptrn equ     0xAA            ;Define the test pattern to be written.

 movlw   .64             ;Initialize that counter.
 movwf   loopcnt         ;
 movlw   write           ;Load W with the Write command.
 movwf   cmd             ;Transfer W into cmd register.
 movlw   tstptrn         ;Intialize the 93C46 data registers with
    ;write data.
 movwf   highb           ;
 movwf   lowb            ;
test1   call    see             ;Write data word into 93C46 device.
 xorlw   error           ;Check completion status.
 btfsc   status,***lag    ;Test for error condition.
 goto    errloop         ;Yes, bad completion status, error-out.
 incf    cmd             ;No, increment the 6 bit memory address
    ;field.
 decfsz  loopcnt         ;Have we written all 64 locations?
 goto    test1           ;No, write another location.

    ;Read loop:

 movlw   .64             ;Initialize loop counter.
 movwf   loopcnt         ;
 movlw   read            ;Load W with the Read command.
 movwf   cmd             ;Transfer W into cmd register.
test2   call    see             ;Read addressed data word from 93C46 device.
 movlw   tstptrn         ;Load W with the pattern written.
 subwf   highb,0         ;Verify the data read against what was
    ;written.
 btfss   status,***lag    ;Same?
 goto    errloop         ;No, error-out.
 movlw   tstptrn         ;Repeat with the lower byte read.
 subwf   lowb,0          ;
 btfss   status,***lag    ;Same?
 goto    errloop         ;No, error-out.
 incf    cmd             ;Yes, both byte correct, increment the 6 bit
    ;memory address field.
 decfsz  loopcnt         ;Have we read all 64 locations?
 goto    test2           ;No, read another location.

allok   goto    allok           ;Home safe!

errloop goto    errloop         ;Bad news!

 END                     ;Thats all folks!