Introduction
OZ 4.7 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.
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 |