mos6522: implement edge-triggering for CA1/2 and CB1/2 control line IRQs
The mos6522 datasheet describes how the control lines IRQs are edge-triggered
according to the configuration in the PCR register. Implement the logic according
to the datasheet so that the interrupt bits in IFR are latched when the edge is
detected, and cleared when reading portA/portB or writing to IFR as necessary.
To maintain bisectibility this change also updates the SCSI, SCSI data, Nubus
and VIA2 60Hz/1Hz clocks in the q800 machine to be negative edge-triggered as
confirmed by the PCR programming in all of Linux, NetBSD and MacOS.
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20220305150957.5053-12-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
diff --git a/hw/misc/mac_via.c b/hw/misc/mac_via.c
index d8b35e6..525e38c 100644
--- a/hw/misc/mac_via.c
+++ b/hw/misc/mac_via.c
@@ -327,7 +327,9 @@
MOS6522State *s = MOS6522(v1s);
qemu_irq irq = qdev_get_gpio_in(DEVICE(s), VIA1_IRQ_60HZ_BIT);
- qemu_set_irq(irq, 1);
+ /* Negative edge trigger */
+ qemu_irq_lower(irq);
+ qemu_irq_raise(irq);
via1_sixty_hz_update(v1s);
}
@@ -338,7 +340,9 @@
MOS6522State *s = MOS6522(v1s);
qemu_irq irq = qdev_get_gpio_in(DEVICE(s), VIA1_IRQ_ONE_SECOND_BIT);
- qemu_set_irq(irq, 1);
+ /* Negative edge trigger */
+ qemu_irq_lower(irq);
+ qemu_irq_raise(irq);
via1_one_second_update(v1s);
}
@@ -917,9 +921,11 @@
* On a Q800 an emulated VIA2 is integrated into the onboard logic. The
* expectation of most OSs is that the DRQ bit is live, rather than
* latched as it would be on a real VIA so do the same here.
+ *
+ * Note: DRQ is negative edge triggered
*/
val &= ~VIA2_IRQ_SCSI_DATA;
- val |= (ms->last_irq_levels & VIA2_IRQ_SCSI_DATA);
+ val |= (~ms->last_irq_levels & VIA2_IRQ_SCSI_DATA);
break;
}
@@ -1146,7 +1152,8 @@
s->a |= (1 << n);
}
- qemu_set_irq(irq, level);
+ /* Negative edge trigger */
+ qemu_set_irq(irq, !level);
}
static void mos6522_q800_via2_init(Object *obj)
