| ??? 01/01/06 04:53 Read: times |
#106324 - External access Responding to: ???'s previous message |
Kevin Timm said:
that's the exact doc I was referencing (though it wasn't mentioned). What I was confused about was the connection to the 'decision' port for each circuit. It's been made clear to me now -- thanks to all :)
One additional query though, I see that you mention that /EA must be kept high in normal use and pulled low for programming. Interestingly, one of the maxim documents I've seen (of course, I can't remember which) shows that 3 circuits should be used instead of 2 (meaning that /EA is only affected in programming mode, and left - effectively - unattached at all other times) Which document is this? It sounds strange. Traditionally, on 8051-based devices, /EA must be high to execute from an internal program store. Apparently, the DS89C420 is no different... "DS89C420 Data Sheet" said:
External Access. Allows selection of internal or external program memory. Connect to ground to force the DS89C420 to use an external memory-program memory. The internal RAM is still accessible as determined by register settings. Connect to VCC to use internal flash memory. As far as I know, leaving /EA floating is not a proper configuration. --Sasha Jevtic |
| Topic | Author | Date |
| ds89c420 programmer | 01/01/70 00:00 | |
| clarification | 01/01/70 00:00 | |
| schematic | 01/01/70 00:00 | |
| Now I understand what you mean... | 01/01/70 00:00 | |
| so, I'm correct? | 01/01/70 00:00 | |
| Yes, you are | 01/01/70 00:00 | |
| not to beat a dead horse | 01/01/70 00:00 | |
| Much more | 01/01/70 00:00 | |
| given | 01/01/70 00:00 | |
thanks | 01/01/70 00:00 | |
| DS89C420 ISP | 01/01/70 00:00 | |
| isp response | 01/01/70 00:00 | |
| External access | 01/01/70 00:00 | |
| caps for crystal | 01/01/70 00:00 | |
| Only NP0 ceramics! | 01/01/70 00:00 | |
| over my head | 01/01/70 00:00 | |
| NP0, X7R, Z5U | 01/01/70 00:00 | |
| digikey will be my friend | 01/01/70 00:00 | |
| Everybody probably already knows | 01/01/70 00:00 | |
| Overlapping standards | 01/01/70 00:00 | |
| holy moly | 01/01/70 00:00 | |
| Oh dear...! | 01/01/70 00:00 | |
| now you're playing me right? | 01/01/70 00:00 | |
| Not really | 01/01/70 00:00 | |
| yes really ;) | 01/01/70 00:00 | |
| one more thing | 01/01/70 00:00 | |
| Sure | 01/01/70 00:00 | |
| max232 charge caps | 01/01/70 00:00 | |
| Yes | 01/01/70 00:00 | |
| a good reference for this . . . | 01/01/70 00:00 | |
| thx | 01/01/70 00:00 |