mirror of https://github.com/hsoft/collapseos.git
89 lines
1.6 KiB
C
89 lines
1.6 KiB
C
#include <stdio.h>
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#include "acia.h"
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static void _check_irq(ACIA *acia)
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{
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// do we have RDRF?
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if ((acia->status & 0x01) && (acia->control & 0x80)) {
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acia->status |= 0x80;
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}
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// do we have TDRE?
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if ((acia->status & 0x02) && ((acia->control & 0xe0) == 0xe0)) {
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acia->status |= 0x80;
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}
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}
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void acia_init(ACIA *acia)
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{
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acia->status = 0x02; // TDRE
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acia->control = 0x00;
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acia->rx = 0;
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acia->tx = 0;
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acia->in_int = false;
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}
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bool acia_has_irq(ACIA *acia)
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{
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if (acia->in_int) {
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return false;
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}
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acia->in_int = acia->status & 0x80;
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return acia->in_int;
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}
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bool acia_cantransmit(ACIA *acia)
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{
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return !(acia->status & 0x01 // RDRF
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|| acia->control & 0x40); // RTS
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}
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bool acia_hastx(ACIA *acia)
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{
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return !(acia->status & 0x02); // TRDE
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}
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uint8_t acia_read(ACIA *acia)
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{
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acia->status |= 0x02; // TRDE high
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_check_irq(acia);
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return acia->tx;
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}
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void acia_write(ACIA *acia, uint8_t val)
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{
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if (acia->control & 0x40) { // RTS high
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fprintf(stderr, "ACIA RTS high: can't send byte\n");
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return;
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}
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acia->status |= 0x01; // RDRF high
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acia->rx = val;
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_check_irq(acia);
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}
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uint8_t acia_ctl_rd(ACIA *acia)
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{
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return acia->status;
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}
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void acia_ctl_wr(ACIA *acia, uint8_t val)
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{
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acia->control = val;
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_check_irq(acia);
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}
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uint8_t acia_data_rd(ACIA *acia)
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{
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acia->status &= ~0x81; // RDRF and IRQ low
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acia->in_int = false;
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return acia->rx;
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}
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void acia_data_wr(ACIA *acia, uint8_t val)
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{
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acia->tx = val;
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acia->status &= ~0x82; // TRDE and IRQ low
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acia->in_int = false;
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_check_irq(acia);
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}
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