;[]---------------------------------------------------------------------------[] ;| | ;| Witham Keyscan Monitor unit | ;| | ;| | ;| AirBorn Electronics, 1998 | ;[]---------------------------------------------------------------------------[] ;This code is copyright (C)1998 AirBorn Electronics .include "8051.H" .ECHO " .." .TITLE "*Witham Keyscan monitor unit, AirBorn 61-2-9925-0325" .ECHO "Witham Keyscan monitor unit, AirBorn 61-2-9925-0325" .ECHO "\n" ;Revision History -------------------------------------------------------- ;9 Oct 1998 Original code ;24 Nov 1998 Prototype tested okay ;[]------------------------[] ;| Constants | ;[]------------------------[] Crystal equ 22118400 ;Crystal frequency RomSize equ 0800h ;RomSize - 2k (0800h) for 89C2051 ChipSpeed equ 1 ;Chip Speed, 1=8051 3=Dallas Hi-Speed #if (ChipSpeed == 1) .ECHO " ..Assembling for standard 8051 with crystal frequency of " #endif .ECHO (Crystal) .ECHO "Hz\n" #if (Crystal > 33000000) .ECHO "Is your crystal really > 33Mhz ??\n" #endif .ECHO " ..Assembling for a ROM size of " .ECHO (RomSize) .ECHO " bytes\n" Baud0A equ 9600 ;Desired baud rate (A) for serial port Baud0B equ 115200 ;Desired baud rate (A) for serial port T1RLA equ (Crystal/(Baud0A*192)) ;Work out correct T1 reload for the baud rate T1RLB equ (Crystal/(Baud0B*192)) ; and correct T1 reload for second baud rate ;Sample rates selected to divide evenly SmpRatA equ 500 ;Sample update rate in Hertz, for switches, A SmpRatB equ 5000 ;Sample update rate in Hertz, for switches, B SmpDiv equ SmpRatB/SmpRatA SmpTime equ 1000000/SmpRatB ;Sample time in microseconds T0Pr equ 20000/SmpRatB ;Find an appropriate prescaler T0RL equ (Crystal/(12*SmpRatB*T0Pr) ;Work out correct T0 reload for sample rate ;[]------------------------[] ;| Input/Output allocation | ;[]------------------------[] DatPort equ P1 ;Port to read keyscan data from GrnLED equ P3.7 ;Signal low (0) lights LED SwPort equ P3 ;Port to read dip switches from SwMask equ 3Ch ;Mask of switch inputs SpeedBit equ 4 ;Dipswitch 1 mask: On=Fast (0) Off=Slow (1) ;[]------------------------[] ;| RAM Memory allocation | ;[]------------------------[] MnRBase equ 00h ;Set the register base address for mainline T0Prsc equ 08h ;Prescaler to time down sample interrupt rate OldSw equ 09h ;History byte for switch settings DivCnt equ 0Ah ;Count down for divider between fast/slow rates StackBase equ 18h ;Start of stack in internal RAM - allow 16 bytes Flag0 equ 28h ;Location for bit flags OldSpd bit (0+((Flag0-20h)*8)) ;Semaphore bit - when set, it is OK to Tx ;[]------------------------[] ;| Reset/Interrupt Vectors | ;[]------------------------[] ORG 0 ;CPU Jumps here at reset ;The .ORG directive starts code at that loc'tn. ;Other assemblers use "CSEG AT 0" ajmp Init ORG 3h ;CPU Calls here on external int 0, if enabled ajmp Stub ORG 0Bh ;CPU Calls here on timer 0 overflow, if enabled djnz T0Prsc,AReti ;Exit if a Sample time has not elapsed yet mov T0Prsc,#T0Pr ;Set the Sample time prescaler to max again ajmp Timer0 ;The program should jump to Timer 0 routine ORG 13h ;CPU Calls here on external int 1, if enabled ;The program should jump to ext int 1 routine ajmp Stub ;INT1 int is not enabled in the example program ; and so should never happen - if it does then ; jump to "stub" ORG 1Bh ;CPU Calls here on timer 1 overflow, if enabled ;The program should jump to Timer 1 routine ajmp Stub ;TF1 int is not enabled in the example program ; and so should never happen - if it does then ; jump to "stub" ORG 23h ;CPU Calls here on Serial interrupt, if enabled ajmp Stub ChkStart: ;ROM checksumming starts from here ;[]------------------------[] ;| Interrupt Routines | ;[]------------------------[] Stub: clr EA ;Unexpected interrupt - disable all ints ;If it is possible to give some indication of ; error, such as lighting an LED, do it here acall AReti ;Flag the interrupt routine is finished ;A "reti" instruction tells the CPU that its ; interrupt routine has finished and it ; should return to the main program. ; However as we "called" the reti the CPU is ; manipulated into returning here, but in an ; "all interrupts finished" condition. ajmp Init ;Re-initialize: So unexpected Int causes reset AReti: reti ;------------------------------------------------------------------------------ Timer0: ;We are here at "SampRate" (In V1.00 = 5000Hz) push PSW ;Save the PSW register push ACC ;Save the Accumulator mov PSW,#MnRBase ;Set to register bank used by mainline mov A,P3 ;Get the dip switch port orl A,#(255-SwMask) ;Mask to see just the valid switches xch A,OldSw ;Exchange with the last switch port read value xrl A,OldSw ;Mask to see if any differences jz Time2 ;Continue if no changes in switch position ;There has been a change in switch position mov A,OldSw ;Fetch the switch settings again anl A,#SpeedBit ;Test the Baud rate setting bit jnz Slow ;Jump if on the slow setting Fast: mov TH1,#(256-T1RLB) ;Init the baud rate timer to fast rate sjmp Time1 Slow: mov TH1,#(256-T1RLA) ;Init the baud rate timer to slow rate Time1: Time2: mov A,OldSw ;Fetch the switch settings again anl A,#SpeedBit ;Test the BaudRate/SampleRate setting bit jz Time3 ;Jump if on the fast setting ;We are on slow setting - need to divide SmpRate djnz DivCnt,Time4 ;Skip next operation if we haven't counted div mov DivCnt,#SmpDiv ;Reload counter to SmpRatB/SmpRatA Time3: mov SBUF,DatPort ;Sample input port, transmit it out the UART Time4: pop ACC ;Restore Acc, previously pushed pop PSW ;Restore PSW, previously pushed reti ;Return ;------------------------------------------------------------------------------ ;[]------------------------[] ;| Setup | ;[]------------------------[] Init: ;Here at initialization mov SP,#(StackBase-1) ;Initialise the Stack pointer clr A ;Clear all RAM mov R0,#7Fh ;Start at location 7Fh - work down mov R1,#7Eh ;Do 7Eh locations - stop before R0/R1 Put0: mov @R0,A ;Clear a byte of RAM dec R0 ;Update the RAM pointer djnz R1,Put0 ;Loop until all locations cleared dec R0 ;Clear location 0 - the last location mov PSW,#MnRBase ;Set active register bank (Regbnk 0: Locs 0-7) ;Init important things mov TMOD,#22h ;T1,T0: 8 bit Auto R/L mov PCON,#80h ;Enables high baud rate generation divisor mov TH1,#(256-T1RLA) ;Initialise Baud rate mov TH0,#(256-T0RL) ;Initialise the sample timer mov T0Prsc,#T0Pr ;Set the Sample time prescaler to max mov TCON,#50h ;Run both timers mov SCON,#50h ;Standard UART settings mov IE,#10000010b ;Enable interrupts: EA, Timer0 ;IE Register Map: EA-x-ET2-ES---ET1-EX1-ET0-EX0 ;[]------------------------[] ;| Main Program | ;[]------------------------[] Main: mov R2,#7 ;Main just flashes the diagnostic LED mov R3,#0 mov R4,#0 Main1: djnz R4,Main1 djnz R3,Main1 djnz R2,Main1 cpl GrnLED sjmp Main ;---------------------------------------------------------------------------- .ECHO " .." .ECHO ($+12) ;Report the number of bytes of code .ECHO " bytes of program memory used = " .ECHO (($*100)/(RomSize-12)) .ECHO "% of total memory capacity\n" .ECHO " .." .ECHO (RomSize-($+12) ;Report the number of bytes of code left .ECHO " bytes of program memory space left unused\n" #if ($>=(RomSize-11)) ;generate an invalid statement to cause an error when we go past end of ROM !!! PROM bounds exceeded #else ;.FILL (RomSize-($+12)) ;Fill the remainder of ROM with 0FFh Version .db "SW V1.00 ",0 .ECHO " ..Firmware V1.00 \n" .CHK ChkStart ;Put an arithmetic checksum in 2nd last byte .ORG (RomSize-1) .db 0AAh #endif END