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https://github.com/hsoft/collapseos.git
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326 lines
8.3 KiB
Forth
326 lines
8.3 KiB
Forth
( Receives keystrokes from PS/2 keyboard and send them to the
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'164. On the PS/2 side, it works the same way as the controller
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in the rc2014/ps2 recipe. However, in this case, what we have
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on the other side isn't a z80 bus, it's the one of the two
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controller ports of the SMS through a DB9 connector.
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The PS/2 related code is copied from rc2014/ps2 without much
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change. The only differences are that it pushes its data to a
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'164 instead of a '595 and that it synchronizes with the SMS
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with a SR latch, so we don't need PCINT. We can also afford to
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run at 1MHz instead of 8.
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*** Register Usage ***
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GPIOR0 flags:
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0 - when set, indicates that the DATA pin was high when we
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received a bit through INT0. When we receive a bit, we set
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flag T to indicate it.
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R16: tmp stuff
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R17: recv buffer. Whenever we receive a bit, we push it in
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there.
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R18: recv step:
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- 0: idle
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- 1: receiving data
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- 2: awaiting parity bit
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- 3: awaiting stop bit
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R19: Register used for parity computations and tmp value in
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some other places
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R20: data being sent to the '164
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Y: pointer to the memory location where the next scan code from
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ps/2 will be written.
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Z: pointer to the next scan code to push to the 595 )
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0x0060 CONSTANT SRAM_START
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0x015f CONSTANT RAMEND
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0x3d CONSTANT SPL
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0x3e CONSTANT SPH
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0x11 CONSTANT GPIOR0
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0x35 CONSTANT MCUCR
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0x33 CONSTANT TCCR0B
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0x3b CONSTANT GIMSK
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0x38 CONSTANT TIFR
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0x32 CONSTANT TCNT0
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0x16 CONSTANT PINB
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0x17 CONSTANT DDRB
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0x18 CONSTANT PORTB
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2 CONSTANT CLK
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1 CONSTANT DATA
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3 CONSTANT CP
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0 CONSTANT LQ
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4 CONSTANT LR
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0x100 100 - CONSTANT TIMER_INITVAL
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( We need a lot of labels in this program... )
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VARIABLE L5 VARIABLE L6 VARIABLE L7 VARIABLE L8
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H@ ORG !
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L1 FLBL, ( main )
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L2 FLBL, ( hdlINT0 )
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( Read DATA and set GPIOR0/0 if high. Then, set flag T.
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no SREG fiddling because no SREG-modifying instruction )
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L2 ' RJMP FLBL! ( hdlINT0 )
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PINB DATA SBIC,
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GPIOR0 0 SBI,
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SET,
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RETI,
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L1 ' RJMP FLBL! ( main )
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R16 RAMEND 0xff AND LDI,
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SPL R16 OUT,
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R16 RAMEND 8 RSHIFT LDI,
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SPH R16 OUT,
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( init variables )
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R18 CLR,
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GPIOR0 R18 OUT,
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( Setup int0
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INT0, falling edge )
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R16 0x02 ( ISC01 ) LDI,
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MCUCR R16 OUT,
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( Enable INT0 )
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R16 0x40 ( INT0 ) LDI,
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GIMSK R16 OUT,
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( Setup buffer )
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YH CLR,
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YL SRAM_START 0xff AND LDI,
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ZH CLR,
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ZL SRAM_START 0xff AND LDI,
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( Setup timer. We use the timer to clear up "processbit"
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registers after 100us without a clock. This allows us to start
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the next frame in a fresh state. at 1MHZ, no prescaling is
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necessary. Each TCNT0 tick is already 1us long. )
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R16 0x01 ( CS00 ) LDI, ( no prescaler )
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TCCR0B R16 OUT,
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( init DDRB )
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DDRB CP SBI,
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PORTB LR CBI,
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DDRB LR SBI,
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SEI,
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L1 LBL! ( loop )
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L2 FLBL, ( BRTS processbit. flag T set? we have a bit to
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process )
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YL ZL CP, ( if YL == ZL, buf is empty )
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L3 FLBL, ( BRNE sendTo164. YL != ZL? buf has data )
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( nothing to do. Before looping, let's check if our
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communication timer overflowed. )
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R16 TIFR IN,
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R16 1 ( TOV0 ) SBRC,
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L4 FLBL, ( RJMP processbitReset, timer0 overflow? reset )
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( Nothing to do for real. )
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L1 ' RJMP LBL, ( loop )
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( Process the data bit received in INT0 handler. )
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L2 ' BRTS FLBL! ( processbit )
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R19 GPIOR0 IN, ( backup GPIOR0 before we reset T )
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R19 0x1 ANDI, ( only keep the first flag )
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GPIOR0 0 CBI,
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CLT, ( ready to receive another bit )
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( We've received a bit. reset timer )
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L2 FLBL, ( RCALL resetTimer )
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( Which step are we at? )
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R18 TST,
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L5 FLBL, ( BREQ processbits0 )
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R18 1 CPI,
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L6 FLBL, ( BREQ processbits1 )
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R18 2 CPI,
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L7 FLBL, ( BREQ processbits2 )
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( step 3: stop bit )
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R18 CLR, ( happens in all cases )
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( DATA has to be set )
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R19 TST, ( was DATA set? )
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L1 ' BREQ LBL, ( loop, not set? error, don't push to buf )
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( push r17 to the buffer )
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Y+ R17 ST,
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L8 FLBL, ( RCALL checkBoundsY )
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L1 ' RJMP LBL,
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L5 ' BREQ FLBL! ( processbits0 )
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( step 0 - start bit )
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( DATA has to be cleared )
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R19 TST, ( was DATA set? )
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L1 ' BRNE LBL, ( loop. set? error. no need to do anything. keep
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r18 as-is. )
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( DATA is cleared. prepare r17 and r18 for step 1 )
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R18 INC,
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R17 0x80 LDI,
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L1 ' RJMP LBL, ( loop )
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L6 ' BREQ FLBL! ( processbits1 )
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( step 1 - receive bit
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We're about to rotate the carry flag into r17. Let's set it
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first depending on whether DATA is set. )
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CLC,
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R19 0 SBRC, ( skip if DATA is cleared )
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SEC,
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( Carry flag is set )
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R17 ROR,
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( Good. now, are we finished rotating? If carry flag is set,
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it means that we've rotated in 8 bits. )
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L1 ' BRCC LBL, ( loop )
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( We're finished, go to step 2 )
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R18 INC,
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L1 ' RJMP LBL, ( loop )
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L7 ' BREQ FLBL! ( processbits2 )
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( step 2 - parity bit )
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R1 R19 MOV,
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R19 R17 MOV,
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L5 FLBL, ( RCALL checkParity )
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R1 R16 CP,
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L6 FLBL, ( BRNE processBitError, r1 != r16? wrong parity )
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R18 INC,
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L1 ' RJMP LBL, ( loop )
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L6 ' BRNE FLBL! ( processBitError )
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R18 CLR,
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R19 0xfe LDI,
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L6 FLBL, ( RCALL sendToPS2 )
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L1 ' RJMP LBL, ( loop )
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L4 ' RJMP FLBL! ( processbitReset )
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R18 CLR,
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L4 FLBL, ( RCALL resetTimer )
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L1 ' RJMP LBL, ( loop )
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L3 ' BRNE FLBL! ( sendTo164 )
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( Send the value of r20 to the '164 )
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PINB LQ SBIS, ( LQ is set? we can send the next byte )
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L1 ' RJMP LBL, ( loop, even if we have something in the
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buffer, we can't: the SMS hasn't read our
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previous buffer yet. )
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( We disable any interrupt handling during this routine.
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Whatever it is, it has no meaning to us at this point in time
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and processing it might mess things up. )
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CLI,
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DDRB DATA SBI,
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R20 Z+ LD,
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L3 FLBL, ( RCALL checkBoundsZ )
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R16 R8 LDI,
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BEGIN,
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PORTB DATA CBI,
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R20 7 SBRC, ( if leftmost bit isn't cleared, set DATA high )
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PORTB DATA SBI,
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( toggle CP )
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PORTB CP CBI,
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R20 LSL,
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PORTB CP SBI,
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R16 DEC,
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' BRNE AGAIN?, ( not zero yet? loop )
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( release PS/2 )
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DDRB DATA CBI,
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SEI,
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( Reset the latch to indicate that the next number is ready )
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PORTB LR SBI,
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PORTB LR CBI,
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L1 ' RJMP LBL, ( loop )
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L2 ' RCALL FLBL! L4 ' RCALL FLBL! L2 LBL! ( resetTimer )
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R16 TIMER_INITVAL LDI,
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TCNT0 R16 OUT,
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R16 0x02 ( TOV0 ) LDI,
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TIFR R16 OUT,
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RET,
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L6 ' RCALL FLBL! ( sendToPS2 )
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( Send the value of r19 to the PS/2 keyboard )
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CLI,
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( First, indicate our request to send by holding both Clock low
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for 100us, then pull Data low lines low for 100us. )
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PORTB CLK CBI,
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DDRB CLK SBI,
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L2 ' RCALL LBL, ( resetTimer )
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( Wait until the timer overflows )
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BEGIN,
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R16 TIFR IN,
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R16 1 ( TOV0 ) SBRS,
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AGAIN,
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( Good, 100us passed. )
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( Pull Data low, that's our start bit. )
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PORTB DATA CBI,
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DDRB DATA SBI,
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( Now, let's release the clock. At the next raising edge, we'll
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be expected to have set up our first bit (LSB). We set up
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when CLK is low. )
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DDRB CLK CBI, ( Should be starting high now. )
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( We will do the next loop 8 times )
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R16 8 LDI,
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( Let's remember initial r19 for parity )
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R1 R19 MOV,
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BEGIN,
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( Wait for CLK to go low )
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BEGIN, PINB CLK SBIC, AGAIN,
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( set up DATA )
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PORTB DATA CBI,
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R19 0 SBRC, ( skip if LSB is clear )
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PORTB DATA SBI,
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R19 LSR,
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( Wait for CLK to go high )
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BEGIN, PINB CLK SBIS, AGAIN,
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16 DEC,
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' BRNE AGAIN?, ( not zero? loop )
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( Data was sent, CLK is high. Let's send parity )
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R19 R1 MOV, ( recall saved value )
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L6 FLBL, ( RCALL checkParity )
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( Wait for CLK to go low )
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BEGIN, PINB CLK SBIC, AGAIN,
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( set parity bit )
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PORTB DATA CBI,
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R16 0 SBRC, ( parity bit in r16 )
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PORTB DATA SBI,
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( Wait for CLK to go high )
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BEGIN, PINB CLK SBIS, AGAIN,
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( Wait for CLK to go low )
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BEGIN, PINB CLK SBIC, AGAIN,
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( We can now release the DATA line )
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DDRB DATA CBI,
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( Wait for DATA to go low, that's our ACK )
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BEGIN, PINB DATA SBIC, AGAIN,
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( Wait for CLK to go low )
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BEGIN, PINB CLK SBIC, AGAIN,
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( We're finished! Enable INT0, reset timer, everything back to
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normal! )
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L2 ' RCALL LBL, ( resetTimer )
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CLT, ( also, make sure T isn't mistakely set. )
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SEI,
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RET,
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L8 ' RCALL FLBL! ( checkBoundsY )
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( Check that Y is within bounds, reset to SRAM_START if not. )
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YL TST,
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IF, RET, ( not zero, nothing to do ) THEN,
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( YL is zero. Reset Z )
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YH CLR,
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YL SRAM_START 0xff AND LDI,
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RET,
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L3 ' RCALL FLBL! ( checkBoundsZ )
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( Check that Z is within bounds, reset to SRAM_START if not. )
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ZL TST,
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IF, RET, ( not zero, nothing to do ) THEN,
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( ZL is zero. Reset Z )
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ZH CLR,
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ZL SRAM_START 0xff AND LDI,
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RET,
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L5 ' RCALL FLBL! L6 ' RCALL FLBL! ( checkParity )
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( Counts the number of 1s in r19 and set r16 to 1 if there's an
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even number of 1s, 0 if they're odd. )
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R16 1 LDI,
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BEGIN,
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R19 LSR,
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' BRCC SKIP, R16 INC, ( carry set? we had a 1 ) TO,
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R19 TST, ( is r19 zero yet? )
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' BRNE AGAIN?, ( no? loop )
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R16 0x1 ANDI,
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RET,
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