Tandy 1000 HX Technical Reference Manual page 58

0060
0061
0062
• TANDY COMPUTER PRODUCTS •
PORT A / KEYBOARD INTERFACE CONTROL PORTS
(READ ONLY)
BIT Description
0 Keyboard Bit 0-LSB
1 Keyboard Bit 1
2 Keyboard Bit 2
3 Keyboard Bit 3
4 Keyboard Bit 4
5 Keyboard Bit 5
6 Keyboard Bit 6
7 Keyboard Bit 7-MSB
PORT B - READ or WRITE
BIT Description
0 1 = 8253 Gate #2 Enable
1 1 = Speaker Data Out Enable
2 Not Used
3 Not Used
4 1 = Disable Internal Speaker
(Sound Control 2)
5 0 = Not Used
6 0 = Not Used
7 1 = Keyboard Clear
PORT C - READ/WRITE:
BITS 4-7
Bits 0-3; READ ONLY:
0063-007F
Address
0080
BIT
0
1
2
3
4
5
6
7
Description
(Output) Not Used
(Output) Not Used
(Output) Not Used
(Output) CPU Clock Rate
0 = 4.77 MHz (PC Compatible Rate)
1 = 7.16 MHz (Default by Boot ROM)
EEPROM Serial Data Read
8253 Out #2
Monochrome Mode
0 = Color Monitor
1 = (Not Supported)
0 = Reserved
Not Used
Description
DMA Page Reg. (Not Used)
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