| ??? 05/27/05 09:07 Read: times |
#93966 - dirty hack... Responding to: ???'s previous message |
... but viable.
Instead of RC I would use a piece of logic (GAL or CPLD) based on a counter clocked by XTAL and reset(*) by ALE; if it would count up to 6 (= ALE off) it would set the output; ALE would reset it. I have read a hack on PSEN, too (http://www.hw.cz/design/51_hw/psen_33.html, but in czech language). Upon doing a MOVC from outside the internal FLASH area (=> works on <64kB FLASH derivatives ONLY) it generates a single pulse on the PSEN pin, so a divide-by-2 clocked from PSEN can be used to have an extra output (reset to RST). The caveat is, that during PSEN the P0 and P2 pins are driven hard to the address (both 1 and 0), so they cannot be used as simple outputs any more; and also using them as inputs is cumbersome... So these are 2 extra outputs, but is it worth the complications... Jan Waclawek (*) OT: english language question: reset, or resetted? Thanks. |
