Post by thread:Interfacing an External Ram to 17c44

Hi, sorry for the long delay - I'm clearing a mail backlog.I didn't see an answer to message posted so here goes. I've just completed a project using the 17c44 in its extended microcontroller mode. I have 32Kram and two memory mapped ADCs connected to the external address/data bus( with '373s for address latch), some memory decoding to keep them apart and '374s for the ADCs to update readings. In this mode the only way I could access the external ram was to treat it as if it were eeprom using the tablrd and tablwrt commands. This works a treat. My memory is addressed from 8000h upwards. What was handy was that my program code could be blasted into the 17C44 windowed device when an update was needed. Alternatively (an option I did not have to use) I allowed for 32k Eprom in the lower half of memory. The problem with this is that I'd have to split the hex file into high and low bytes - one for each eprom. Luckily MPLAB can facilitate this but I'm glad I didn't have to investigate this further (as I don't have an eprom programmer!) Hope this helps John ----------------------------------------------------- John Walshe spam_OUTwalshejTakeThisOuTnmrc.ucc.ie National Microelectronics Research Centre, Prospect Row, Cork, Ireland. Direct Line: + 353 21 904082 Switch: + 353 21 903000 Fax: + 353 21 270271 Home page: http://nmrc.ucc.ie/ ------------------------------------------------------

John Walshe wrote: > > Hi, sorry for the long delay - I'm clearing a mail backlog.I didn't see an > answer to message posted so here goes. > > I've just completed a project using the 17c44 in its extended > microcontroller mode. I have 32Kram and two memory mapped ADCs connected to > the external address/data bus( with '373s for address latch), some memory > decoding to keep them apart and '374s for the ADCs to update readings. > > In this mode the only way I could access the external ram was to treat it as > if it were eeprom using the tablrd and tablwrt commands. This works a treat. > My memory is addressed from 8000h upwards. > > What was handy was that my program code could be blasted into the 17C44 > windowed device when an update was needed. > > Alternatively (an option I did not have to use) I allowed for 32k Eprom in > the lower half of memory. The problem with this is that I'd have to split > the hex file into high and low bytes - one for each eprom. Or you can use a 16 BITS DATA eprom {Quote hidden}> Luckily MPLAB can > facilitate this but I'm glad I didn't have to investigate this further (as I > don't have an eprom programmer!) > > Hope this helps > John > ----------------------------------------------------- > > John Walshe .....walshejKILLspam@spam@nmrc.ucc.ie > > National Microelectronics Research Centre, > Prospect Row, Cork, Ireland. > > Direct Line: + 353 21 904082 > Switch: + 353 21 903000 > Fax: + 353 21 270271 > > Home page: http://nmrc.ucc.ie/ > ------------------------------------------------------