📄 rs232.asm
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;******************************************************************
; RS232的传送与接收子程序 修改自serialb.asm
;******************************************************************
;label: XPAGEON
;
; Variable memory allocations
innerDelayOneCount: equ 3Ch ; Delay One: Inner delay count
outerDelayOneCount: equ 3Dh ; Delay One: Outer delay count
innerDelayCount: equ 3Eh ; Delay: Inner delay count
outerDelayCount: equ 3Fh ; Delay: Outer delay count
rxEnable: equ 40h ; Receiver Enabled Flag
rxBitCount: equ 42h ; Recieve Bits Count
rxFrameCount: equ 4dh ; Recieve Frame Count
rxData: equ 46h ; Receive Data Holding Register
rxBufPtr: equ 48h ; Receive Buffer Pointer
rxFrameFlag: equ 4Ah ; Framing Error Flag (0=No,1=Yes)
rxPassCount: equ 4Bh ; Transmit Buffer Pointer
rxBuf: equ 50h ; Recieve Buffer Start
rxBufEnd: equ 5Fh ; Recieve Buffer End
txEnable: equ 4eh ; Transmiter Enabled Flag
txBitCount: equ 43h ; Transmit Bits Count
txFrameCount: equ 45h ; Transmit Frame Count
txData: equ 47h ; Transmit Data Holding Register
txBufPtr: equ 49h ; Transmit Buffer Pointer
txBuf: equ 4Ch ; Transmit Buffer Start (4 Bytes)
;
; Constant declarations
; Transmit counter values
txStart: equ 00h ; Start bit begin
txBit0: equ 03h ; Start bit end
txBit1: equ 07h ; Data bit 0 end
txBit2: equ 0Ah ; Data bit 1 end
txBit3: equ 0Dh ; Data bit 2 end
txBit4: equ 10h ; Data bit 3 end
txBit5: equ 14h ; Data bit 4 end
txBit6: equ 17h ; Data bit 5 end
txBit7: equ 1Ah ; Data bit 6 end
txStop: equ 1Dh ; Data bit 7 end
txComp: equ 20h ; Stop bit end
;
txDataMask: equ FEh ; Mask to preserve inputs.
;
; Receive counter values
rxStart: equ 01h ; Start bit center
rxBit0: equ 05h ; Data bit 0 center
rxBit1: equ 09h ; Data bit 1 center
rxBit2: equ 0Ch ; Data bit 2 center
rxBit3: equ 0Fh ; Data bit 3 center
rxBit4: equ 12h ; Data bit 4 center
rxBit5: equ 16h ; Data bit 5 center
rxBit6: equ 19h ; Data bit 6 center
rxBit7: equ 1Ch ; Data bit 7 center
rxStop: equ 1Fh ; Data bit 7 center
rxComp: equ 22h ; Stop bit center
lastrxBit: equ 07h ; Last receive data bit count
;4
; Interrupt masks
GPIO_intMask: equ 40h ; Mask for Port 0 GPIO interrupts.
128us_intMask: equ 02h ; Mask to enable 128us only.
;
; ASCII Characters for commands
Car_Ret: equ 0Dh ; Carriage Return Terminator
Ln_Fd: equ 0Ah ; Line Feed Terminator
Asc_Space: equ 20h ; ASCII Space Character
;
;************************************************************************
; If we are recieving a byte of data from the serial channel we need to
; go to the receive subroutine.
Serial_ISR:
push A ;
push X ;
; mov A, [rxEnable] ; Load the receive enable flag.
; cmp A, 0 ; Check for receive in progress.
; jnz Increment_rxFrameCount ; Yes, go receive.
;************************************************************************
; If we are sending a byte of data to the serial channel we need to
; go to the transmit subroutine.
;
mov A, [txEnable] ; Check for transmit in progress.
cmp A, 0 ;
jnz Increment_txFrameCount ; Yes, go transmit.
jmp done_Serial ; Default
;
; We are transmitting.
Increment_txFrameCount:
inc [txFrameCount] ; Adjust frame count.
mov A, [txFrameCount] ; Put it in the accumulator
mov [txBitCount], A ; Save it as the new bit count
jmp done_Serial ; Finished
;
; We are receiving.
;Increment_rxFrameCount:
inc [rxFrameCount] ; Adjust frame count.
call rxRoutine ; Go get a character
pop X ;
mov A, 00h ; Disable interrupts and return.
ipret Global_Interrupt ;
;
; Finish the interrupt handling
done_Serial:
pop X
mov A, 128us_intMask ; Load 128us ISR Enable value
ipret Global_Interrupt ; Return and enable 128us ISR
;
;************************************************************************
; The GPIO interrupt will occur at the start of a receive data byte.
; The low going start bit will trigger the GPIO_ISR.
;
GPIO_ISR:
push A ; save the accumulator to stack
push X ; save X on stack
; Three steps for detecting the start bit:
; 1.) Check that the receiver generated the interrupt.
; iord [Port0_Data]
; and A, 80h
; jz GPIO_ISR_Done
; jnz GPIO_ISR_Done
; 2.) Set the receive enable bit.
mov A, 01h ; Load the accumulator.
mov [rxEnable], A ; write to the receive enable flag.
;
; 3.) Clear the receive data register.
mov A, 00h ; Clear the accumulator.
mov [rxData], A ; Clear the receive data register.
GPIO_ISR_Done:
pop x ; Restore the index register.
mov A, 128us_intMask ; Load the 128us interrupt mask.
ipret Global_Interrupt ; Return to caller.
; 128us interrupt enabled.
;
;************************************************************************
; During serial transfers data bit 0 is transmitted first.
; We will use Port 0 Bit 7 for receive and Bit 0 for transmit.
; Data will always be right shifted for either transmit or receive.
; Port 0 Bit 7 will be a falling edge sensitive GPIO_ISR input.
; Port 0 bits 6-0 and Port 1 bits 3-0 will be outputs.
;
SerialInitialize:
push A ; Save the accumulator.
push X ; Save the index.
mov A, FFh ; load accumulator with ones
iowr Port0_Data ; output ones to port 0
iowr Port1_Data ; output ones to port 1
mov A, 00h ; load accumulator with zeros
iowr Port0_Pullup ; enable port 0 pullups
iowr Port1_Pullup ; enable port 1 pullups
;
iowr Port0_Interrupt ; disable port 0 interrupts
iowr Port1_Interrupt ; disable port 1 interrupts
;
mov A, 08h ; load accumulator with med sink
iowr Port0_Isink0 ; minimum sink current Port0 bit 0
;
; iowr Watchdog ; clear watchdog timer
;
; Clear the serial channel counters.
mov A, 00h
mov [rxEnable], A ; Clear rxEnable Flag
mov [rxBitCount], A ; Clear rx bit count.
mov [rxFrameCount], A ; Clear rx frame counter.
mov [rxBufPtr], A ; Clear rx buffer Pointer.
mov [txEnable], A ; Clear txEnable Flag.
mov [txBitCount], A ; Clear tx bit count.
mov [txFrameCount], A ; Clear tx frame counter.
mov [txBufPtr], A ; Clear tx buffer Pointer.
mov A, 81h ; Enable port0 bit7 as input.
iowr Port0_Data ; All other bits are outputs.
mov A, 7Eh ; Select falling edge interrupt
iowr Port0_Pullup ; on port0 bit7.
mov A, 00h ;
iowr Port0_Interrupt ; Disable port 0 bit 7 interrupt.
mov [txBufPtr], A ; Reset tx buffer pointer.
; mov [interrupt_mask], A ; Default all interrupts to disabled.
pop X ; Restore the index.
pop A ; Restore the accumulator.
ret ; Return to caller.
;************************************************************************
; TX_Data processing:
; This routine will write a byte of data.
; 1.) Send the active low Start bit.
; 2.) Send eight variable data bits.
; 3.) Send the active high Start bit.
; 4.) Stay in transmit until complete.
;************************************************************************
;
txRoutine:
; Prepare for the transmit.
push A ; save accumulator.
mov A, 01h ; Load txEnable Flag.
mov [txEnable], A ; Store txEnable Flag.
mov A, [txFrameCount] ; Get frame count.
mov [txBitCount], A ; Save bit count.
;
sendStart:
; Write out the start bit. (active low)
mov A, FEh ; Load tx Start bit.
iowr Port0_Data ; Send tx Start bit.
mov A, 02h ; Load 128us ISR Enable value.
iowr Global_Interrupt ; Enable 128us ISR.
;
; Check the bit count and send a bit if required.
check_tx_bit:
mov A, [txBitCount] ; Get frame count
cmp A, txBit0 ; tx bit 0 at frame count=03h
jz sendtxBit ; Go send data bit
cmp A, txBit1 ; tx bit 1 at frame count=07h
jz sendtxBit ; Go send data bit
cmp A, txBit2 ; tx bit 2 at frame count=0Ah
jz sendtxBit ; Go send data bit
cmp A, txBit3 ; tx bit 3 at frame count=0Dh
jz sendtxBit ; Go send data bit
cmp A, txBit4 ; tx bit 4 at frame count=10h
jz sendtxBit ; Go send data bit
cmp A, txBit5 ; tx bit 5 at frame count=14h
jz sendtxBit ; Go send data bit.
cmp A, txBit6 ; tx bit 6 at frame count=17h.
jz sendtxBit ; Go send data bit.
cmp A, txBit7 ; tx bit 7 at frame count=1Ah.
jz sendtxBit ; Go send data bit.
cmp A, txStop ; tx Stop at frame count=1Dh.
jz sendStop ; Go send stop bit.
cmp A, txComp ; tx Stop at frame count=20h.
jz txEnd ; Go send end transmit.
jmp check_tx_bit ; Wait for the next interrupt.
;
sendtxBit:
; Transmit the current data bit and adjust for next pass.
mov A, [txData] ; Get the current data.
or A, txDataMask ; Mask out inputs.
iowr Port0_Data ; Output the current data bit.
mov A, [txData] ; Get the current data.
asr A ; Align next data bit.
mov [txData], A ; Save adjusted data.
mov A, FFh ; Fill the accumulator.
mov [txBitCount], A ; Write to bit counter.
jmp check_tx_bit ; Wait for next bit time.
;
sendStop:
; The data has been sent, now send the stop bit.
mov A, FFh ; Load stop bit.
iowr Port0_Data ; Send stop bit.
jmp check_tx_bit ; Go to end of transmit.
;
txEnd:
; The last data bit has been sent.
; Clean up and return.
; mov A, 00h ; Clear the accumulator.
; mov [interrupt_mask],A ; Load into the mask.
mov a,[interrupt_mask]
iowr Global_Interrupt ; Disable all interrupts.
mov A, 00h ; Load tx Start bit.
mov [txBitCount], A ; Clear tx bit count.
mov [txFrameCount], A ; Clear tx frame counter.
mov [txEnable], A ; Clear the tx enadle flag.
mov [rxFrameCount], A ; Clear rx frame counter.
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