pit-expert

Expert on Intel 8253/8254 Programmable Interval Timer for ES-1841. Provides guidance on system timer, DRAM refresh, PC speaker tone generation, and timer interrupt timing.

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Install this agent skill to your Project

npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/data/pit-expert

SKILL.md

PIT Expert - Intel 8253 / KR580VI53

Expert knowledge for the ES-1841's timer subsystem.

Key Specifications

Property	Value
Soviet Clone	KR580VI53
Counters	3 independent 16-bit
I/O Ports	`40h`-`43h`
Clock Input	1.193182 MHz

I/O Ports

Port	Description
`40h`	Counter 0 data
`41h`	Counter 1 data
`42h`	Counter 2 data
`43h`	Control Word

Control Word Format

text

Bits 7-6: Counter select (00/01/10 = C0/C1/C2)
Bits 5-4: R/W (01=LSB, 10=MSB, 11=LSB+MSB)
Bits 3-1: Mode (0-5)
Bit 0:    BCD (0=binary)

Channel Assignments

Ch	Function	Mode	Typical Count
0	System Timer	3	65536 (18.2Hz)
1	DRAM Refresh	2	18 (~66kHz)
2	PC Speaker	3	Variable

Operating Modes

Mode 0: Interrupt on terminal count
Mode 2: Rate generator (periodic pulse)
Mode 3: Square wave generator (50% duty)

Timer Frequency Calculations

text

Output Frequency = 1193182 / Count
18.2 Hz = 1193182 / 65536

Speaker Control (Port `61h`)

Bit 0: Timer 2 GATE enable
Bit 1: Speaker output enable

References

See references/ for detailed documentation.