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next-cube: separate rtc read and write shift logic

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Introduce a new next_rtc_cmd_is_write() function to determine if an rtc command
is a read or write, and start by using it to avoid shifting the rtc input value
if a rtc read command is executed.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Thomas Huth <huth@tuxfamily.org>
Message-ID: <20241222130012.1013374-21-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Thomas Huth <huth@tuxfamily.org>
This commit is contained in:
Mark Cave-Ayland 2024-12-22 12:59:59 +00:00 • committed by Thomas Huth
parent 825ac12564
commit b37da8b95f
1 changed files with 76 additions and 66 deletions
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16
hw/m68k/next-cube.c
View file

@ -165,6 +165,12 @@ static void next_scr2_led_update(NeXTPC *s)
} }
} }
static bool next_rtc_cmd_is_write(uint8_t cmd)
{
return (cmd >= 0x80 && cmd <= 0x9f) ||
(cmd == 0xb1);
}
static void next_scr2_rtc_update(NeXTPC *s) static void next_scr2_rtc_update(NeXTPC *s)
{ {
uint8_t old_scr2, scr2_2; uint8_t old_scr2, scr2_2;
@ -186,13 +192,18 @@ static void next_scr2_rtc_update(NeXTPC *s)
((scr2_2 & SCR2_RTDATA) ? 1 : 0); ((scr2_2 & SCR2_RTDATA) ? 1 : 0);
} }
if (rtc->phase >= 8 && rtc->phase < 16) { if (rtc->phase >= 8 && rtc->phase < 16) {
if (next_rtc_cmd_is_write(rtc->command)) {
/* Shift in value to write */
rtc->value = (rtc->value << 1) | rtc->value = (rtc->value << 1) |
((scr2_2 & SCR2_RTDATA) ? 1 : 0); ((scr2_2 & SCR2_RTDATA) ? 1 : 0);
} else {
/* Shift out value to read */
/* if we read RAM register, output RT_DATA bit */ /* if we read RAM register, output RT_DATA bit */
if (rtc->command <= 0x1F) { if (rtc->command <= 0x1F) {
scr2_2 = scr2_2 & (~SCR2_RTDATA); scr2_2 = scr2_2 & (~SCR2_RTDATA);
if (rtc->ram[rtc->command] & (0x80 >> (rtc->phase - 8))) { if (rtc->ram[rtc->command] &
(0x80 >> (rtc->phase - 8))) {
scr2_2 |= SCR2_RTDATA; scr2_2 |= SCR2_RTDATA;
} }
@ -246,7 +257,6 @@ static void next_scr2_rtc_update(NeXTPC *s)
case 0x26: case 0x26:
ret = SCR2_TOBCD((info->tm_year - 100)); ret = SCR2_TOBCD((info->tm_year - 100));
break; break;
} }
if (ret & (0x80 >> (rtc->phase - 8))) { if (ret & (0x80 >> (rtc->phase - 8))) {
@ -255,7 +265,7 @@ static void next_scr2_rtc_update(NeXTPC *s)
rtc->retval = (rtc->retval << 1) | rtc->retval = (rtc->retval << 1) |
((scr2_2 & SCR2_RTDATA) ? 1 : 0); ((scr2_2 & SCR2_RTDATA) ? 1 : 0);
} }
}
} }
rtc->phase++; rtc->phase++;