The '''8253''' and '''8254''' are general purpose timer chips, each containing three 16bit timers.
== 8253 vs 8254 ==
8253 and 8254 are basically the same: both are pin-compatible and software compatible. The difference is that the 8254 supports higher clock frequencies, and it includes a readback feature for the control registers (which are write-only on 8253).
== Usage in CPC interfaces ==
Also used by [[Aleste 520EX]] CPC clone:
F4X0h Aleste PPI Port A, 8253 Baudrate Timer 0 (RX Clock) (W) F4X1h Aleste PPI Port A, 8253 Baudrate Timer 1 (TX Clock) (W) F4X2h Aleste PPI Port A, 8253 ColorSet Timer 2 (FUTURE) (W) F4X3h Aleste PPI Port A, 8253 Timer 0-2 Control Registers (W)
Clock Input for RX/TX is 4MHz, Clock output goes to a [[8251 USART chip]],
Clock Output may be further divided by 1, 16, or 64 in the 8251 chip,