; Micro Basics RS-232 Serial<-->Parallel Transceiver ; By: Adam Davis, Spring 2000 ; For more information, including an almost complete ; data sheet, please see http://www.ubasics.com/ ; This file and the following may change (We reserve ; the right to do that ;-), please check the afore- ; mentioned website for updates periodically. ; Micro Basics and Adam Davis do not provide any ; warranty or gurantee as to the fitness of this code ; for any particular application or use, and to not ; accept any liability for its use or misuse. ; This file is released into the public domain with ; the following usage restrictions: ; Any item sold with this code (or more than 80% of ; this code) must include (in either electronic or ; paper form) this exact file with no changes, or the ; most recent version of this file to be found on ; www.ubasics.com or officially distributed by Micro ; Basics or Adam Davis unless written permission has ; been granted by Adam Davis or by an executive of ; Micro Basics. This file must be prominently placed. ; 'Item' shall be defined as, but not limited to, any ; device, record, book, electronic communication, or ; any medium or method which could hold this code in ; any form. 'Sold' shall be taken to mean any ; transaction taking place between two or more ; individuals or businesses in which goods, money, or ; other material/information is mutually exchanged. ; My interpretation is simply: ; Don't sell this without giving your customer the ; 1) knowledge of who created it ; 2) ability to make them ; Don't bundle this with any product without the entire ; code. ; A large portion of this code came from the book ; "Serial PIC'n", Square One, Roger L. Stevens, without ; which this construction would have taken much longer. ; While not required, I'm acknowleging his contribution. ; I heartily recommend this book as an addition to ; every PIC hobbyist's bookshelf. ; Please note that I like my tabs to be 3 spaces. The ; comments (and even code) will appear to be spaced ; 'weirdly' when viewed at the normal tab spacing of 8. radix hex list p=16c54 ; #DEFINE InvertRS232 ; Comment this out for true RS232 __CONFIG H'000A' ; Bit 3: Code Protect (0 for on) ; Bit 2: Watch Dog Timer (1 for on) ; Bits 1 & 0: ; 11 = RC osc ; 10 = HS osc ; 01 = XT osc ; 00 = LP osc ; c equ 0 z equ 2 ; Carry dc equ 1 ; Zero pd equ 3 ; Digit Carry to equ 4 ; Power Down ; w equ 0 ; Working register flag f equ 1 ; File register flag ; ;------------------------------------------------------------------------ indf equ 00 ; Indirect file register tmr0 equ 01 ; Timer pcl equ 02 ; Program Counter status equ 03 ; Status Register fsr equ 04 ; Indirect data pointer porta equ 05 ; Port A portb equ 06 ; Port B ;------------------------------------------------------------------------- comflg equ 0008 ; Communications flags dlyctr equ 0009 ; Delay Counter recreg equ 000A ; Receive Register recuse equ 000B ; Receive User Register rloop equ 000C ; Receive Loop Counter rbit equ 000D ; Receive Bit Counter xmtreg equ 000E ; Transmit Register xmtuse equ 000F ; Transmit User Register xloop equ 0010 ; Transmit Loop Counter xbit equ 0011 ; Transmit Bit Counter ; useflg equ 0012 ; User Flags (not used?) myflag equ 0013 ; My Flags trisreg equ 0014 ; Copy of Tris B lochost equ 0015 ; Local/Host register ; ;--------------------------------------------------------------------------- recflg equ 00 ; Receive Flag lbflg equ 01 ; Last Bit Flag feflg equ 02 ; Framing Error Flag ndrflg equ 03 ; New Data Received Flag roflg equ 04 ; Receive Overrun Flag xmtflg equ 05 ; Xmitting Flag xdrflg equ 06 ; Xmit Data Ready Flag xcflg equ 07 ; Xmit Complete Flag lochospin equ 03 ; Bit for Local/Host Flag dirpin equ 02 ; Bit for direction pin lbi equ 00 ; Last Byte was Instruction Flag setup equ 01 ; Re-Initialize flag ; outport equ porta ; Xmit is Port A:1 outpin equ 01 inport equ porta ; Receive is Port A:0 inpin equ 00 ;---------------------------------------------------------------------------- org 0x1ff ; Reset Vector for 16C54 goto start org 0x00 ; start clrf porta ifdef InvertRS232 bcf outport,outpin ; Output marking else bsf outport,outpin ; Output marking endif clrf portb movlw 0xFD tris porta ; Port A all input except bit 1 movlw 0xFF ; Set PORTB as inputs movwf trisreg tris portb clrf comflg ; Clear all com flags bsf comflg,xcflg ; Set Xmit Completed Flag (MUST DO!) bsf myflag, setup ; Make sure we go through setup first thing bcf myflag, lbi ; Clear Last Bit Instruction flag goto frec ; Start RECV/XMIT/USER cycle (21/19/12 cycles) ;--------------------------------------------------------------------------- ; include taskfull.grp ;====== TASKFULL.GRP ======================================================= ;------RECEIVE ROUTINE 21 cycles-------------------------------------------- rdeld set rdele ; Delay rdeld is the same as delay rdele ; frec btfss comflg,recflg ; Currently Receiveing? If yes, skip next goto frec2 ; No. Go see if we have a start bit yet decfsz rloop,f ; Yes. Update loop counter. ; If bit is complete skip next. goto rdelb ; Bit not complete. Delay and exit. btfsc comflg,lbflg ; Last bit flag set? If no, skip next goto frec3 ; Yes. Go complete byte. bsf status,c ; No. Read bit (set carry) ifdef InvertRS232 btfsc inport,inpin ; Is b3 = 1? If yes, skip next else btfss inport,inpin ; Is b3 = 1? If yes, skip next endif bcf status,c ; No. Clear Carry. rrf recreg,f ; Rotate carry to received byte. movlw 04 ; Initialize loop counter movwf rloop decfsz rbit,f ; Update rbit counter. ; Skip next if all 8 bits done. goto rdele ; Not all 8 are done. Delay and exit btfss comflg,ndrflg ; New data received flag clear? If yes, skip next bsf comflg,roflg ; No. Set receive overrun flag. bsf comflg,lbflg ; Set last bit flag movf recreg,w ; Move received byte to user receive register movwf recuse goto rdelf ; Delay and exit ; frec2 ifdef InvertRS232 btfss inport,inpin ; Start bit? If yes, skip next. else btfsc inport,inpin ; Start bit? If yes, skip next. endif goto rdela ; No. Delay and exit bsf comflg,recflg ; Yes. Set receiving flag movlw 08 ; Initialize receive bit counter movwf rbit movlw 05 ; Initialize receive loop counter movwf rloop goto rdelc ; Delay and exit ; frec3 ifdef InvertRS232 btfss inport,inpin ; Stop bit? If no, skip next else btfsc inport,inpin ; Stop bit? If no, skip next endif goto frec4 ; Yes. Skip next instruction. bsf comflg,feflg ; Set Framing error flag frec4 bcf comflg,recflg ; Clear receiving flag bcf comflg,lbflg ; Clear last bit flag bsf comflg,ndrflg ; Set new data received flag goto rdeld ; Delay and Exit. rdelb nop ; This is the setup/initialization routine. ; It is run inbetween bit readings and between bytes. ; It is possible for the operate routine (after xmit routine) ; to be run before this setup. If so, and if any setup ; changes needed to be made beforehand it could mess ; things up. This can only occur when the received stop ; bit is less than 3/4 of one bit time. rdela btfss myflag, setup ; Setup flag? If yes, skip next goto dlysetup ; Delay and exit btfsc porta, lochospin ; Local or host? If local(0), skip next goto host ; Host(1). Goto host setup bcf myflag, lochospin ; Clear the local/host flag movlw 00FD ; Set the dir pin as input tris porta btfsc porta, dirpin ; Direction in(0) or out(1)? If in, skip next goto localout ; Out, goto local out setup movlw 00FF ; In. Set portB as inputs. tris portb movwf trisreg ; Copy tris B settings to trisreg bcf myflag, setup ; Clear the setup flag SupE goto fxmt ; 2 1 ; Goto transmit routine host movlw 00F9 ; Set direction pin as output tris porta bcf porta, dirpin ; Clear direction pin, signifying input movlw 00FF ; Set portb as inputs (safest route) tris portb movwf trisreg ; Copy portb tris to trisreg bcf myflag, setup ; Clear the setup flag nop ; Delay goto fxmt ; Goto transmit routine dlysetup ; Various delays used in both the nop ; 12 ; receive and setup routines nop ; 11 nop ; 10 rdelc nop ; 9 rda2 goto rdele ; 8 7 rdele goto rda3 ; 6 5 rda3 goto rda4 ; 4 3 rda4 goto rdelf ; 2 1 localout movlw 0000 ; Set portB as output tris portb movwf trisreg ; Copy portb tris to trisreg bcf myflag, setup ; Clear setup flag nop ; Delay (transmit routine next rdelf ;----TRANSMIT ROUTINE 19 cycles----------------------------------------------------- fxmt btfss comflg,xmtflg ; Transmitting? If yes, skip next goto fxmt2 ; No. Go see if we need to be. decfsz xloop,f ; Yes. Update loop counter. ; If bit completed skip next goto xdlyb ; Bit not completed. Delay and exit movlw 04 ; Initialize loop counter movwf xloop decfsz xbit,f ; Update bit counter. ; Skip next if all bits completed. goto fxmt4 ; Not all bits done. Go send next bit. bcf comflg,xmtflg ; All bits sent. Clear xmit flag. bsf comflg,xcflg ; Set xmit complete flag goto xdlyc ; Delay and exit ; fxmt2 btfss comflg,xdrflg ; xmit data ready? If yes, skip next goto xdlya ; No. Delay and exit. bsf comflg,xmtflg ; Yes. Set xmiting flag. movlw 0a ; Initialize bit counter. movwf xbit movlw 04 ; Initialize loop counter. movwf xloop movf xmtuse,w ; Move user data to xmit register. movwf xmtreg bcf comflg,xdrflg ; Clear xmit data ready flag. goto fxd1 ; Cycle equalizer fxd1 ifdef InvertRS232 bsf outport,outpin ; Start bit. else bcf outport,outpin ; Start bit. endif nop nop nop nop nop nop nop goto fxmt8 ; Delay and exit. ; ; fxmt4 bsf status,c ; Set Carry rrf xmtreg,f ; Move data bit to Carry ; fxmt5 ifdef InvertRS232 btfss status,c ; Carry (data bit) = 0 ? If yes, skip next else btfsc status,c ; Carry (data bit) = 0 ? If yes, skip next endif goto fxmt6 ; No. data bit = 1. Set Pin a:1 bcf outport,outpin ;Yes. Data bit =0. Clear port a1 goto fxmt7 ; Delay & exit fxmt6 bsf outport,outpin ; set port A:1 nop ; Cycle Equalizer fxmt7 nop nop nop nop nop nop nop goto fxmt8 ; Delay & exit ; ; xdlyc goto fxd4 ; 6 5 ; Various delays for xmit routine fxd4 goto fxd5 ; 4 3 fxd5 nop nop nop nop nop nop nop goto fxmt8 ; 2 1 match1 movlw 00FF ; Set Tris B as inputs bsf porta, dirpin ; Dirpin = high (input) goto main1 ; Go back to main operate routine nomatch nop goto main2 ; Delay and exit DoHostOut btfss myflag, lbi ; Last byte instruction? If yes, skip next goto operF ; Delay and exit btfss trisreg, 0 ; Tris B as input? If yes, skip next goto operA ; No. Delay and exit btfss comflg, xcflg ; Yes. Is transmitter ready? If yes, skip next. goto operE ; No. Delay and exit. movf portb, w ; Copy Port B to xmtuse movwf xmtuse bcf comflg, xcflg ; Clear Xmit completed flag bsf comflg, xdrflg ; Set Xmit data ready flag bcf myflag, lbi ; Clear last byte instruction flag goto main2 ; Go back to main operate routine DoHostIn btfsc trisreg,0 ; Is port b set as output? If yes, skip next. goto operA ; No. Delay and exit movf recuse, w ; Move byte from receive register to port b movwf portb bcf porta, dirpin ; Yes. Set the direction pin low to show output. bcf myflag, lbi ; Clear last byte instruction flag. nop nop nop goto main2 ; Go back to main operate routine. dolocal btfsc porta, dirpin ; Is the direction pin low? If yes, skip next. goto localin ; No. Go to input routine. movlw 00FF ; Set port b as input tris portb movwf trisreg ; Copy port b tris to trisreg btfss comflg, xcflg ; Is the transmitter free? If yes, skip next. goto operC ; No. Delay and exit movf portb,w ; Yes. Move port B to xmit register. movwf xmtuse bcf comflg, xcflg ; Clear xmit complete flag bsf comflg, xdrflg ; Set xmit-ready flag goto operD ; Delay and exit localin movlw 0000 ; Set port b as outputs tris portb movwf trisreg ; Copy port b tris to trisreg btfss comflg, ndrflg ; New data received? If yes, skip next. goto operE ; No. Delay and exit movf recuse, w ; Copy received data to port b. movwf portb bcf comflg, ndrflg ; Clear the new data received flag. goto operD ; Delay and exit operF nop ; Various delay points for the operate routine nop operA nop operC nop operE nop operB nop nop nop operD nop goto fxmt8 xdlyb nop ; 20 xdlya btfss porta, lochospin ; Skip next if HOST goto dolocal ; Locah/Host pin is low (local control) btfss comflg, ndrflg ; Skip next if there is a character waiting goto DoHostOut ; No character waiting, do nothing. btfsc myflag, lbi ; Skip next if the last character was NOT '1' or '2' goto DoHostIn ; The last character tells me to perform a hosted function movlw '1' ; Put '1' into W for a comparison test xorwf recuse, w ; If recuse matches '1' then W will be 0. btfsc status, z ; Skip next if W is not zero goto match1 ; W was zero, set up PORTB, etc movlw '2' ; W was not zero, put '2' into W for comparison xorwf recuse, w ; If recuse matches '2' then W will be zero now btfss status, z ; Skip next if W is zero goto nomatch ; W was not zero, no match, we'll exit. movlw 0000 ; Set W to 0000, which will go into trisB and make it output main1 tris portb ; Set port b to all output movwf trisreg ; Copy setting to trisreg for directional use later bsf myflag, lbi ; Set the 'Last Byte was Instruction' flag main2 bcf comflg, ndrflg ; Reset the receiver ; fxmt8 ; ;----------------------------------------------------------------------------- ;dloop decfsz dlyctr,f ; goto dloop ; retlw 0 ;----------------------------------------------------------------------------- ; ;------USER ROUTINE 12 cycles------------------------------------------------- echo movf porta, w ; Copy port A to w. andlw 0008 ; Mask w so that pin a:3 is left alone, all others are cleared xorwf lochost,w ; Test lochost register against w. ; If they are the same, w will be zero btfsc status, z ; Are they the same? If yes, skip next. bsf myflag, setup ; Set setup flag uda3 goto frec ;Last line of user dloop decfsz dlyctr,f ;3n+5 (includes call statement and return) goto dloop retlw 0 ;----------------------------------------------------------------------- end ;-----------------------------------------------------------------------