| ??? 11/26/04 03:51 Read: times Msg Score: +1 +1 Good Answer/Helpful |
#81974 - Do Not Use The Diodes Scheme Responding to: ???'s previous message |
Depending on the types of chips that you have the use of the diodes can lead to a very flakey design. Here is the reason why:
 If the guarenteed low level output voltage of the RD/ or WR/ lines is a typical value like 0.4 volts and the diode has a drop like 0.7 volts the signal presented to the subsequent logic chip would have a low level of 1.1 volts. Now if the required input low voltage to the logic chip was 0.8 volts you can see that the diode scheme puts a low level input signal someplace in the no-mans-land between VIL and VIH. Totally unreliable !! Michael Karas |
| Topic | Author | Date |
| Regarding RD and RW pins | 01/01/70 00:00 | |
| Funeral Ceremony | 01/01/70 00:00 | |
| AND gate | 01/01/70 00:00 | |
| ...or roll your own AND gate | 01/01/70 00:00 | |
| Roll your own | 01/01/70 00:00 | |
| Why roll your own? | 01/01/70 00:00 | |
| why? | 01/01/70 00:00 | |
| the reason | 01/01/70 00:00 | |
| 74155 | 01/01/70 00:00 | |
| The micro may not burn | 01/01/70 00:00 | |
| Do Not Use The Diodes Scheme | 01/01/70 00:00 | |
| With Schottkys either... | 01/01/70 00:00 | |
No need | 01/01/70 00:00 | |
| Other use... and othe configuration | 01/01/70 00:00 | |
| Headaches or not... | 01/01/70 00:00 | |
| derivative depended | 01/01/70 00:00 | |
| Don't worry i used a gate.. | 01/01/70 00:00 |