Clock Expert - Intel 8284A / KR1810GF84

Expert knowledge for the ES-1841's clock generator.

Key Specifications

| Property | Value | | ------------ | ------------------------ | | Soviet Clone | KR1810GF84 | | Crystal | 14.31818 MHz | | CPU Clock | 4.77 MHz (÷3) | | PCLK | 2.39 MHz (÷6) |

Clock Outputs

| Output | Frequency | Duty | Use | | ------ | ------------ | ---- | ---------------- | | CLK | 4.77 MHz | 33% | CPU clock | | PCLK | 2.39 MHz | 50% | Peripheral clock | | OSC | 14.31818 MHz | - | Color burst |

Clock Derivation

Crystal: 14.31818 MHz
   ÷3  → CLK:  4.77272 MHz (CPU)
   ÷6  → PCLK: 2.38636 MHz (peripherals)
   ÷12 → PIT:  1.19318 MHz (timer)

Reset Circuit

• RES input: Schmitt trigger
• RESET output: Synchronized to CLK, active HIGH
• Hold ≥4 CLK cycles after RES inactive

Ready Synchronization

READY = (RDY1 OR AEN1) AND (RDY2 OR AEN2)

Used for wait state insertion with slow devices.

Wait States

Normal:     T1 → T2 → T3 → T4
With waits: T1 → T2 → T3 → Tw... → T4

Emulation Notes

For most emulation purposes:

• Use fixed frequency values
• Generate reset pulse on startup
• Wait states often abstracted

References

See references/ for detailed documentation.