collapseos/blk/588
Virgil Dupras a9ed8da0b2 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.
2020-08-14 22:58:05 -04:00

12 lines
370 B
Plaintext

: 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) ;