70 lines
1.6 KiB
Forth
70 lines
1.6 KiB
Forth
( ACIA
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Manage I/O from an asynchronous communication interface adapter
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(ACIA). provides "EMIT" to put c char on the ACIA as well as
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an input buffer. You have to call "~ACIA" on interrupt for
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this module to work well.
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CONFIGURATION
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ACIA_CTL: IO port for the ACIA's control registers
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ACIA_IO: IO port for the ACIA's data registers
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ACIA_MEM: Address in memory that can be used variables shared
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with ACIA's native words. 8 bytes used.
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)
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0x20 CONSTANT ACIABUFSZ
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( Points to ACIA buf )
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: ACIA( [ ACIA_MEM 4 + LITN ] ;
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( Points to ACIA buf end )
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: ACIA) [ ACIA_MEM 6 + LITN ] ;
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( Read buf pointer. Pre-inc )
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: ACIAR> [ ACIA_MEM LITN ] ;
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( Write buf pointer. Post-inc )
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: ACIAW> [ ACIA_MEM 2 + LITN ] ;
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( This means that if W> == R>, buffer is full.
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If R>+1 == W>, buffer is empty. )
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: ACIA$
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H@ DUP DUP ACIA( ! ACIAR> !
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1+ ACIAW> ! ( write index starts one position later )
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ACIABUFSZ ALLOT
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H@ ACIA) !
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( setup ACIA
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CR7 (1) - Receive Interrupt enabled
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CR6:5 (00) - RTS low, transmit interrupt disabled.
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CR4:2 (101) - 8 bits + 1 stop bit
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CR1:0 (10) - Counter divide: 64
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)
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0b10010110 ACIA_CTL PC!
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( setup interrupt )
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( 4e == INTJUMP )
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0xc3 0x4e RAM+ C! ( JP upcode )
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['] ~ACIA 0x4f RAM+ !
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(im1)
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;
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: KEY
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( inc then fetch )
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ACIAR> @ 1+ DUP ACIA) @ = IF
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DROP ACIA( @
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THEN
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( As long as R> == W>-1, it means that buffer is empty )
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BEGIN DUP ACIAW> @ = NOT UNTIL
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ACIAR> !
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ACIAR> @ C@
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;
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: EMIT
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( As long at CTL bit 1 is low, we are transmitting. wait )
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BEGIN ACIA_CTL PC@ 0x02 AND UNTIL
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( The way is clear, go! )
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ACIA_IO PC!
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;
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