# CPU board

## Components
- CPU: [W65C02](../datasheets/w65c02s.pdf)
- RAM: [LY62256PL-5LL](../datasheets/LY62256PL-55LL.pdf)
- ROM: [AT28C64B](../datasheets/AT28C64B.pdf)
- Register: [74HC377](../datasheets/74HC_HCT377.pdf)

## Register
- Address 0x5FFF/0b0101_1111_1111_1111
- decode using [74HC20](../datasheets/74HC20.pdf), [74HC00](../datasheets/74hc00.pdf) 
- $b_{15},\dots,b_0$
- $\overline E=\neg(b_0\land b_1\land b_2\land b_3)\land\neg(b_4\land b_5\land b_6\land b_7)\land\neg(b_8\land b_9\land b_{10}\land b_{11})\land\neg(b_{12}\land b_{14})\land (b_{13}\lor b_{15})$

## Timings
- PHI2 target: 10MHz -> 100ns