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Comments in expansion unit code

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This commit is contained in:
Jasmine Iwanek
2022-01-23 18:41:00 -05:00
parent cdf6fa118a
commit c0be4ce3d5
1 changed files with 19 additions and 5 deletions
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24
src/device/ibm_5161.c
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@@ -54,15 +54,29 @@ ibm_5161_in(uint16_t port, void *priv)
ret = dev->regs[port & 0x0007];
switch (port) {
case 0x211:
case 0x215:
case 0x210: /* Write to latch expansion bus data (ED0-ED7) */
/* Read to verify expansion bus data (ED0-ED7) */
break;
case 0x214: /* Write to latch data bus bits (DO - 07) */
/* Read data bus bits (DO - D7) */
break;
case 0x211: /* Read high-order address bits (A8 - A 15) */
case 0x215: /* Read high-order address bits (A8 - A 15) */
ret = (get_last_addr() >> 8) & 0xff;
break;
case 0x212:
case 0x216:
case 0x212: /* Read low-order address bits (A0 - A7) */
case 0x216: /* Read low-order address bits (A0 - A7) */
ret = get_last_addr() & 0xff;
break;
case 0x213:
case 0x213: /* Write 00 to disable expansion unit */
/* Write 01 to enable expansion unit */
/* Read status of expansion unit
00 = enable/disable
01 = wait-state request flag
02-03 = not used
04-07 = switch position
1 = Off
0 =On */
ret = dev->regs[3] & 0x01;
break;
}