collapseos/blk/588

: ACIA$
    H@ [ ACIA( LITN ] ! 0 [ ACIAR> LITN ] C!
    1 [ ACIAW> LITN ] C! ( write index starts one pos later )
    [ ACIA_BUFSZ LITN ] ALLOT
( 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 LITN ] PC!
    (im1) ;
acia: make wholly cross compilable 2020-05-12 11:52:44 +10:00			`: ACIA$`
acia: simplify driver The previous approach of maintaining R> and W> pointers was conceptually simple, but made INT handler code actually quite complex. Now, we maintain indexes instead. It's much easier to perform bounds checks and to compare for equality, something we have to do quick in the INT handler. 2020-08-15 12:51:27 +10:00			`H@ [ ACIA( LITN ] ! 0 [ ACIAR> LITN ] C!`
			`1 [ ACIAW> LITN ] C! ( write index starts one pos later )`
			`[ ACIA_BUFSZ LITN ] ALLOT`
acia: make wholly cross compilable 2020-05-12 11:52:44 +10:00			`( 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 LITN ] PC!`
			`(im1) ;`