SC2200 datasheet(308/433 Pages) NSC

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308

Revision 3.0

Core Logic Module (Continued)

I/O Port 042h

Write

PIT Timer 2 Counter (Speaker)

7:0

Counter Value.

Read

PIT Timer 2 Status (Speaker)

Counter Output. State of counter output signal.

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.

BCD Mode.

0: Binary.

1: BCD (Binary Coded Decimal).

I/O Port 043h (R/W)

PIT Mode Control Word Register

Notes:

If bits [7:6] = 11: Register functions as Read Status Command and:

Bit 5 = Latch Count

Bit 4 = Latch Status

Bit 3 = Select Counter 2

Bit 2 = Select Counter 1

Bit 1 = Select Counter 0

Bit 0 = Reserved

If bits [5:4] = 00: Register functions as Counter Latch Command and:

Bits [7:6] = Selects Counter

Bits [3:0] = Don’t care

7:6

Counter Select.

00: Counter 0.

01: Counter 1.

10: Counter 2.

11: Read-back command (Note 1).

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.

BCD Mode.

0: Binary.

1: BCD (Binary Coded Decimal).

Table 5-45. Programmable Interval Timer Registers (Continued)

Bit

Description

SC2200 Datasheet(PDF) 308 Page - National Semiconductor (TI)

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