Introduction
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| Inputs Enable Select | Outputs | |||
|---|---|---|---|---|
| /E /CE | A1 | A0 A19 | /Y1 /CE1 FLASH | /Y0 /CE0 RAM |
| 0 | 0 | 0 | 1 | 0 |
| 0 | 0 | 1 | 0 | 1 |
| 1 | X | X | 1 | 1 |
Logic Diagram
Original
Cut Down Version
Logic Lab Test v Truth Table
| Inputs Enable Select | Outputs | |||
|---|---|---|---|---|
| /E /CE | A0 A19 | /Y1 /CE1 FLASH | /Y0 /CE0 RAM | |
| 00 | 0 | 0 | 1 | 0 |
| 01 | 0 | 1 | 0 | 1 |
| 02 | 1 | 0 | 1 | 1 |
| 03 | 1 | 1 | 1 | 1 |
00
01
02
03
They both agree.
Circuit Diagram
Timings
Trawling through the datasheets for NAND gates found the following:-
| Part No | Chip | Manufacture | Speed | Package | Price | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | Typ | Max | |||||||||||||
| 1085297 | 74HCT00D | NXP | 10nS | SOIC | 0.221 | ||||||||||
| 381755 | 74HCT00N | NXP | 10nS | DIP | 0.667 | ||||||||||
| 9590889 | 74HC00 | Ti | 8nS | DIP | 0.31 | ||||||||||
| 1105915 | SN74AHCIG00 | Ti | 5,2 | 8 mA | SOT-23-5 | 1.78 | |||||||||
| 1287697 | SN74LVCIG007 SN74LVC1G00DBVR | Ti | 4.0 | 32mA | SOT-23-5 | 1.98 | |||||||||
| SN74LVC1G00-EP | Ti | 1.0 | 4.0 | ||||||||||||
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The individual NAND gates are displaying the fastest times. Here is an example:-
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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 |