collapseos/drv/acia.fs

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( ACIA
Manage I/O from an asynchronous communication interface adapter
(ACIA). provides "EMIT" to put c char on the ACIA as well as
an input buffer. You have to call "~ACIA" on interrupt for
this module to work well.
CONFIGURATION
ACIA_CTL: IO port for the ACIA's control registers
ACIA_IO: IO port for the ACIA's data registers
)
0x20 CONSTANT ACIABUFSZ
( Points to ACIA buf )
(sysv) ACIA(
( Points to ACIA buf end )
(sysv) ACIA)
( Read buf pointer. Pre-inc )
(sysv) ACIAR>
( Write buf pointer. Post-inc )
(sysv) ACIAW>
( This means that if W> == R>, buffer is full.
If R>+1 == W>, buffer is empty. )
: ACIA$
H@ DUP DUP ACIA( ! ACIAR> !
1 + ACIAW> ! ( write index starts one position later )
ACIABUFSZ ALLOT
H@ ACIA) !
( setup ACIA
CR7 (1) - Receive Interrupt enabled
CR6:5 (00) - RTS low, transmit interrupt disabled.
CR4:2 (101) - 8 bits + 1 stop bit
CR1:0 (10) - Counter divide: 64
)
0b10010110 ACIA_CTL PC!
( setup interrupt )
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( 4e == INTJUMP )
0xc3 0x4e RAM+ C! ( JP upcode )
['] ~ACIA 0x4f RAM+ !
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(im1)
;
: KEY
( As long as R> == W>-1, it means that buffer is empty )
BEGIN ACIAR> @ 1 + ACIAW> @ = NOT UNTIL
ACIAR> @ C@
1 ACIAR> +!
;
: EMIT
( As long at CTL bit 1 is low, we are transmitting. wait )
BEGIN ACIA_CTL PC@ 0x02 AND UNTIL
( The way is clear, go! )
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ACIA_IO PC!
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;