|
;********************************************************************
;* 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.
zflag 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, zflag ;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,zflag ;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,zflag ;Same?
goto errloop ;No, error-out.
movlw tstptrn ;Repeat with the lower byte read.
subwf lowb,0 ;
btfss status,zflag ;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!
| 
《匠人手记》推荐网上购书渠道： 
匠人学习：
