| ??? 05/09/07 14:54 Modified: 05/09/07 14:57 Read: times |
#138906 - not if he does not decode P2 Responding to: ???'s previous message |
doesn't that mean that the address decoder requires to have 00 at P2 at the moment of /RD-/WR is active?
at movx @Ri P2 in the classic '51 emit the P2 port values. There is a risk using P2 for switches since at the movx @Ri the strong pullup is briefly activated, however using it for LEDs should be problem free as 'pullup is not pulling anything up'. To use it for switches, this after carefully reading the datsheet may be possible if a small resistor is inserted in series with the switches. I do not recall any datasheet stating the value of the strong piullup, but it could not hurt to check. once more this refer to the classic '51 Erik |
| Topic | Author | Date |
| Bus | 01/01/70 00:00 | |
| the answer is \"that depends\" | 01/01/70 00:00 | |
| Maybe a DIP switch | 01/01/70 00:00 | |
| Erik is right with MOVX @A | 01/01/70 00:00 | |
| you surely meant... | 01/01/70 00:00 | |
| not if he does not decode P2 | 01/01/70 00:00 | |
Bus | 01/01/70 00:00 |