32579BCore Logic Module - ISA Legacy Register Space

 

 

Table 6-45. Programmable Interval Timer Registers

Bit

Description

 

 

 

I/O Port 040h

 

 

 

 

Write

 

PIT Timer 0 Counter

 

 

7:0

Counter Value.

 

 

 

Read

 

PIT Timer 0 Status

 

 

7

Counter Output. State of counter output signal.

 

 

6

Counter Loaded. Indicates if the last count written is loaded.

 

0:

Yes.

 

1:

No.

 

 

5:4

Current Read/Write Mode.

 

00: Counter latch command.

 

01: R/W LSB only.

 

10: R/W MSB only.

 

11: R/W LSB, followed by MSB.

 

 

3:1

Current Counter Mode. 0-5.

 

 

0

BCD Mode.

 

0:

Binary.

 

1: BCD (Binary Coded Decimal).

 

 

 

I/O Port 041h

 

 

 

 

Write

 

PIT Timer 1 Counter (Refresh)

 

 

7:0

Counter Value.

 

 

 

Read

 

PIT Timer 1 Status (Refresh)

 

 

7

Counter Output. State of counter output signal.

 

 

6

Counter Loaded. Indicates if the last count written is loaded.

 

0:

Yes.

 

1:

No.

 

 

5:4

Current Read/Write Mode.

 

00: Counter latch command.

 

01: R/W LSB only.

 

10: R/W MSB only.

 

11: R/W LSB, followed by MSB.

 

 

3:1

Current Counter Mode. 0-5.

 

 

0

BCD Mode.

 

0:

Binary.

 

1: BCD (Binary Coded Decimal).

 

 

 

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AMD Geode™ SC1200/SC1201 Processor Data Book

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AMD SC1200, SC1201 manual Programmable Interval Timer Registers