majiayu000 PPI Expert - Intel 8255A / KR580VV55A
Expert knowledge for the ES-1841's peripheral interface.
Key Specifications
| Property | Value |
|---|---|
| Soviet Clone | KR580VV55A |
| I/O Ports | 60h-63h |
| Ports | 3 × 8-bit (A, B, C) |
I/O Port Mapping
| Port | Direction | Function |
|---|---|---|
60h |
Input | Keyboard scan code |
61h |
Output | System control |
62h |
Input | System status |
63h |
Write | Control register |
Port B (61h) - System Control
| Bit | Function |
|---|---|
| 0 | Timer 2 GATE (speaker) |
| 1 | Speaker data enable |
| 4 | RAM parity check enable |
| 5 | I/O channel check enable |
| 6 | Keyboard clock low |
| 7 | Keyboard clear/enable |
Port C (62h) - Status
| Bit | Function |
|---|---|
| 0 | Timer 2 output state |
| 4 | RAM parity error (0=error) |
| 5 | I/O channel check |
Control Word (Port 63h)
Mode set (bit 7 = 1):
- Bit 4: Port A direction (1=input)
- Bit 1: Port B direction (1=input)
Bit set/reset (bit 7 = 0):
- Bits 3-1: Bit select (PC0-PC7)
- Bit 0: Set (1) or Reset (0)
Keyboard Interface
- Scan code arrives at Port A
- IRQ1 triggered
- CPU reads port
60h - Toggle Port B bit 7 to acknowledge
References
See references/ for detailed documentation.