| ??? 06/29/05 19:07 Read: times |
#96225 - PORT2 during MOVX @Ri Responding to: ???'s previous message |
Sasha Jevtic said:
But it is also possible to do MOVX with 8-bit indirect addressing (e.g., MOVX A,@R0). In this case, during the external memory access, port 2 is left in whatever state it was prior to the external memory access. If you require a particular value on port 2 (for a high address byte) when using this type of addressing, you must manually set port 2 prior to the move. True, true, but one more subtlety: while at the 16-bit external memory addressing (MOVC, MOVX @DPTR, program fetch) the whole PORT2 is output strong - both 0s and 1s; when doing the MOVX @Ri (8-bit addressing), PORT2 remains as usual, i.e. esentially open collector with the weak pullups. Jan Waclawek |
| Topic | Author | Date |
| function of 8051 pins | 01/01/70 00:00 | |
| double functions | 01/01/70 00:00 | |
| a requirement | 01/01/70 00:00 | |
| Yeah... and it's really big too! :) | 01/01/70 00:00 | |
| port0 | 01/01/70 00:00 | |
| thanks | 01/01/70 00:00 | |
| do not SHOUT | 01/01/70 00:00 | |
| A couple more little things | 01/01/70 00:00 | |
| PORT2 during MOVX @Ri | 01/01/70 00:00 | |
| which should'nt be a problem | 01/01/70 00:00 | |
| Same thought, almost same time | 01/01/70 00:00 | |
| Port 2 in memory access | 01/01/70 00:00 | |
| double function of SBUF | 01/01/70 00:00 | |
thank you jan waclawek | 01/01/70 00:00 |