;********************************************************************** ; * ; Filename: wirercvr.asm * ; Date: 23 Nov 1999 * ; File Version: 2 * ; * ; Author: Chris White (whitecf@bcs.org.uk) * ; Company: Monitor Computing Services Ltd. * ; * ;********************************************************************** ; * ; Copyright (C) 1999 Monitor Computing Services Ltd. * ; * ; This program is free software; you can redistribute it and/or * ; modify it under the terms of the GNU General Public License * ; as published by the Free Software Foundation; either version 2 * ; of the License, or any later version. * ; * ; This program is distributed in the hope that it will be useful, * ; but WITHOUT ANY WARRANTY; without even the implied warranty of * ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * ; GNU General Public License for more details. * ; * ; You should have received a copy of the GNU General Public * ; License (http://www.gnu.org/copyleft/gpl.html) along with this * ; program; if not, write to: * ; The Free Software Foundation Inc., * ; 59 Temple Place - Suite 330, * ; Boston, MA 02111-1307, * ; USA. * ; * ;********************************************************************** ; * ; Notes: Bod test program excersising simple receiving telemetry * ; interface via asynchronous serial @ 5K baud. * ; * ; 'Wire' interface, asynchronous serial @ 5K baud * ; Port A 4 - Rx, 3 - Tx * ; * ; * ; Data nibbles are received as individual bytes. In each * ; received byte the 'low' nibble gives the data nibble's * ; 'address', 0 - 15, and the 'high' nibble the data * ; nibble's data value. * ; This receiver takes the data nibbles with address values * ; of 0 and 1 and combines their data values to form a * ; single output byte (address 0 == output byte low nibble, * ; address 1 == output byte high nibble). Addresses other * ; than 0 and 1 indicate data for nodes further 'down' the * ; 'data stream' and are forwarded after having 2 (the * ; number of data nibbles used by this receiver) subtracted * ; from their address. * ; As a guard against corruption any data nibble must be * ; received twice in succession with the same value before * ; it is used to modify the output byte value. * ; * ;********************************************************************** ;********************************************************************** ; Include and configuration directives * ;********************************************************************** list p=16C84 #include __CONFIG _CP_OFF & _WDT_OFF & _PWRTE_ON & _XT_OSC ; '__CONFIG' directive is used to embed configuration data within .asm file. ; The lables following the directive are located in the respective .inc file. ; See respective data sheet for additional information on configuration word. #include ;********************************************************************** ; Constant definitions * ;********************************************************************** PORTASTATUS EQU B'00000000' ; Initial port status, all bits set as output PORTBSTATUS EQU B'00000000' ; Initial port status, all bits set as output RTCCINT EQU 158 ; 1Mhz / 100 (adjusted for RTCC write inhibit) = 10Khz INT5KBIT EQU 2 ; Interrupts per serial bit @ 5K baud INT5KINI EQU 3 ; Interrupts per initial Rx serial bit @ 5K (start bit) INT2K5BIT EQU 4 ; Interrupts per serial bit @ 2K5 baud INT2K5INI EQU 6 ; Interrupts per initial Rx serial bit @ 2K5 (start bit) INTMILLI EQU 10 ; Interrupts per millisecond CLKPORT EQU PORTA ; Clock tick output port CLKBIT EQU 2 ; Clock tick output on Port A bit 2 ; 'Up' interface constants RXUFLAG EQU 0 ; 'Up' receive byte buffer 'loaded' status bit RXUERR EQU 1 ; 'Up' receive error status bit RXUBREAK EQU 2 ; 'Up' received 'break' status bit TXUFLAG EQU 3 ; 'Up' transmit byte buffer 'clear' status bit TXUTRIS EQU TRISA ; 'Up' side Tx port direction register TXUPORT EQU PORTA ; 'Up' side Tx port data register TXUBIT EQU 3 ; Tx on Port A bit 3 RXUTRIS EQU TRISA ; 'Up' side Rx port direction register RXUPORT EQU PORTA ; 'Up' side Rx port data register RXUBIT EQU 4 ; Rx on Port A bit 4 ; Telemetry constants OUTPORT EQU PORTB LOWMASK EQU 0x0F ; Mask to isolate low 'nibble' of byte HIGHMASK EQU 0xF0 ; Mask to isolate high 'nibble' of byte ADDRMASK EQU 0x0E ; Mask to identify data not for this 'node' ;********************************************************************** ; Variable definitions * ;********************************************************************** CBLOCK 0x0C ; Status and accumulator storage registers pclath_isr ; PCLATH register store during ISR w_isr ; 'w' register, accumulator, store during ISR status_isr ; status register store during ISR ; Interface registers serStatus ; Serial I/F status flags ; 'Up' side interface registers serURxTmr ; Interrupt counter for serial bit timing serURxReg ; Data shift register serURxByt ; Data byte buffer serURxBitCnt ; Bit down counter serUTxTmr ; Interrupt counter for serial bit timing serUTxReg ; Data shift register serUTxByt ; Data byte buffer serUTxBitCnt ; Bit down counter ; Telemetry registers telemData ; Received telemtry data for forwarding or outputting last0Low ; Last received data for byte 0 low nibble last0High ; Last received data for byte 0 high nibble outData ; Output data value ENDC ;********************************************************************** ; Reset vector * ;********************************************************************** ORG 0x000 ; Processor reset vector BootVector goto Main ; Jump to beginning of program ;********************************************************************** ; Interrupt vector * ;********************************************************************** ORG 0x004 ; Interrupt vector location IsrVector goto BeginISR ; Jump to interrupt service routine ;********************************************************************** ; Link and interface routine macro invocations * ;********************************************************************** EnableRxU EnableRx RXUTRIS, RXUPORT, RXUBIT return InitRxU InitRx serURxTmr, serStatus, RXUFLAG, RXUERR, RXUBREAK return SrvcRxU ServiceRx serURxTmr, RXUPORT, RXUBIT, serURxBitCnt, INT5KINI, serStatus, RXUERR, RXUBREAK, serURxReg, serURxByt, RXUFLAG, INT5KBIT EnableTxU EnableTx TXUTRIS, TXUPORT, TXUBIT return InitTxU InitTx serUTxTmr, serStatus, TXUFLAG return SrvcTxU ServiceTx serUTxTmr, serStatus, serUTxByt, serUTxReg, TXUFLAG, serUTxBitCnt, INT5KBIT, TXUPORT, TXUBIT, 0, 0 LinkURx SerURx SerialRx serStatus, RXUFLAG, serURxByt LinkUTx SerUTx SerialTx serStatus, TXUFLAG, serUTxByt ;********************************************************************** ; Interrupt service routine (ISR) code * ;********************************************************************** BeginISR movwf w_isr ; Save off current W register contents movf STATUS,W ; Move status register into W register movwf status_isr ; save off contents of STATUS register movf PCLATH,W ; Move PCLATH register into W register movwf pclath_isr ; save off contents of PCLATH register btfss INTCON,T0IF ; Skip if RTCC interrupt flag is set ... goto EndISR ; ... otherwise jump to end of service routine BANKSEL TMR0 ; Ensure register page 0 is selected #ifdef CLKPORT bcf CLKPORT,CLKBIT ; Set clock outData low #endif bcf INTCON,T0IF ; Clear the RTCC interrupt bitflag movlw RTCCINT addwf TMR0,F ; Reload RTCC call SrvcRxU ; Perform up interface Rx service call SrvcTxU ; Perform up interface Tx service #ifdef CLKPORT bsf CLKPORT,CLKBIT ; Set clock outData high #endif EndISR movf pclath_isr,W ; Retrieve copy of PCLATH register movwf PCLATH ; Restore pre-isr PCLATH register contents movf status_isr,W ; Retrieve copy of STATUS register movwf STATUS ; Restore pre-isr STATUS register contents swapf w_isr,F swapf w_isr,W ; Restore pre-isr W register contents retfie ; Return from interrupt ;********************************************************************** ; Main program code * ;********************************************************************** Main clrf PORTA ; Clear I/O ports clrf PORTB BANKSEL OPTION_REG ; Select register page 1 movlw PORTASTATUS ; Program I/O port bit directions movwf TRISA movlw PORTBSTATUS movwf TRISB clrf OPTION_REG bsf OPTION_REG,NOT_RBPU bsf OPTION_REG,INTEDG bsf OPTION_REG,PSA BANKSEL TMR0 ; Select register page 0 movlw PORTASTATUS ; For Port A need to write one to each bit ... movwf PORTA ; ... being used for input ; Initialise variables ; Initialise serial link SerInit serStatus, serUTxTmr, serUTxReg, serUTxByt, serUTxBitCnt, serURxTmr, serURxReg, serURxByt, serURxBitCnt call EnableRxU call InitRxU call EnableTxU call InitTxU clrf telemData clrf last0Low clrf last0High clrf outData ; Initialise interrupts movlw RTCCINT movwf TMR0 ; Load RTCC clrf INTCON bsf INTCON,T0IE ; Enable RTCC interrupts bsf INTCON,GIE ; Enable interrupts Rxloop call LinkURx ; Check for data from 'up stream' node btfss STATUS,Z ; Skip if data received ... goto Rxloop ; ... otherwise keep waiting movwf telemData ; Save received telemetry data andlw ADDRMASK ; Isolate address part of received data btfss STATUS,Z ; Skip if address is 0 or 1 ... goto ForwardData ; ... otherwise forward data on 'down stream' btfsc telemData,0 ; Skip address is 0 ... goto GotHigh ; ... otherwise received high nibble data GotLow movf telemData,W ; Retrieve received data xorwf last0Low,W ; Compare with last received low nibble data btfsc STATUS,Z ; Skip, and ignore, if values different ... goto SetLow ; ... otherwise set output low nibble value movf telemData,W ; Retrieve received data and ... movwf last0Low ; ... save as last received low nibble data goto Rxloop SetLow swapf telemData,W ; Get received data part into low nibble ... andlw LOWMASK ; ... and isolate low nibble ... movwf telemData ; ... then store isolated low nibble value movf outData,W ; Get current output data ... andlw HIGHMASK ; ... and isolate high nibble value goto SetOutput GotHigh movf telemData,W ; Retrieve received data xorwf last0High,W ; Compare with last received high nibble data btfsc STATUS,Z ; Skip, and ignore, if values different ... goto SetHigh ; ... otherwise set output high nibble value movf telemData,W ; Retrieve received data and ... movwf last0High ; ... save as last received high nibble data goto Rxloop SetHigh movf telemData,W ; Get received data part into high nibble ... andlw HIGHMASK ; ... and isolate high nibble ... movwf telemData ; ... then store isolated high nibble value movf outData,W ; Get current output data ... andlw LOWMASK ; ... and isolate low nibble value SetOutput iorwf telemData,W ; Combine current and new nibble values ... movwf outData ; ... save as current output data ... movwf OUTPORT ; ... and output value goto Rxloop ; Wait for more data from 'up stream' node ForwardData decf telemData,F ; Decrement, twice, address part of data decf telemData,F Txloop movf telemData,W ; Get telemetry data ... movwf FSR ; ... into FSR in order to transmit call LinkUTx ; Attempt to transmit telemetry data btfss STATUS,Z ; Skip if data sent ... goto Txloop ; ... otherwise keep trying to transmit goto Rxloop ; Wait for more data from 'up stream' node end ; directive 'end of program'