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CMOS addressing; reads and writes

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This commit is contained in:
Dan Luu 2013-03-21 10:45:13 -04:00
parent 22fd4d8cff
commit c9023f6453
1 changed files with 7 additions and 1 deletions
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8
CMOS.js
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@ -27,7 +27,10 @@ function CMOS(PC) {
} }
CMOS.prototype.ioport_write = function(mem8_loc, data) { CMOS.prototype.ioport_write = function(mem8_loc, data) {
if (mem8_loc == 0x70) { if (mem8_loc == 0x70) {
this.cmos_index = data & 0x7f; // the high order bit is used to indicate NMI masking
// low order bits are used to address CMOS
// the index written here is used on an ioread 0x71
this.cmos_index = data & 0x7f;
} }
}; };
CMOS.prototype.ioport_read = function(mem8_loc) { CMOS.prototype.ioport_read = function(mem8_loc) {
@ -35,10 +38,13 @@ CMOS.prototype.ioport_read = function(mem8_loc) {
if (mem8_loc == 0x70) { if (mem8_loc == 0x70) {
return 0xff; return 0xff;
} else { } else {
// else here => 0x71, i.e., CMOS read
data = this.cmos_data[this.cmos_index]; data = this.cmos_data[this.cmos_index];
if (this.cmos_index == 10) if (this.cmos_index == 10)
// flip the UIP (update in progress) bit on a read
this.cmos_data[10] ^= 0x80; this.cmos_data[10] ^= 0x80;
else if (this.cmos_index == 12) else if (this.cmos_index == 12)
// Always return interrupt status == 0
this.cmos_data[12] = 0x00; this.cmos_data[12] = 0x00;
return data; return data;
} }