Introduction
Some games that run in RAM, particularly when in combination with OZ v4.6 and later - running in slot 1, fails to run on the 512K/512K Flash/RAM Card due to a timing error which is introduced by the decode chip CD74HCT139. This is one of the fastest decode chips but it is too slow for our purposes.
The object of this exercise is to see if by redefining the design, a faster decode is achieved.
Tiny url http://tinyurl.com/jdp3qqr
Truth Table
| Inputs Enable Select | Outputs | |||
|---|---|---|---|---|
| /E | A1 | A0 | /Y1 | /Y0 |
| 0 | 0 | 0 | 1 | 0 |
| 0 | 0 | 1 | 0 | 1 |
| 1 | X | X | 1 | 1 |
Logic Diagram
Original
Cut Down Version
Circuit Diagram
Note: Please check the timings of this circuit.
Extra components required
| Component | Manufacturer Part No | Order Code | Price | Min Qty |
|---|---|---|---|---|
N95BT | Maplin | 4.09 | 1 | |
| YA29G | Maplin | 1.79 | 1 | |
| MFR3 2K2 FC | 1565301 | £0.085 | 10 |