Agent skill
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.
Install this agent skill to your Project
npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/other/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
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
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.
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