Post by thread:Extending memory

On Tue, 10 Nov 1998, [iso-8859-1] André Malafaya Baptista wrote: > Hi all. > I think that I know the answer to this (_stupid_) question as I read the > datasheet: > is there any way (and I really mean ANY way) to extend program and data > memory on the 16F84? A few kilobytes extra would be extremely useful... Sure ! Stretch the chip in a vise then fill the cracks with epoxy and use ;) Seriously, if you want a large programming space investigate interpreters of simple languages running on a PIC with program storage in an external EEPROM or several. Disadvantages: speed, code security, 3rd party programming tools or high degree of experience required to make it work. Advantages: too many to quote. Peter

NO, NO At least no way which is transparant to the programmer. For data space, you could attach any kind of RAM (serial RAM is often used) and use your own put / get routines. For code space idem (EEPROM instead of RAM), but you would have to add an interpreter. regards, Wouter. ---------- {Quote hidden}> From: AndrŽ Malafaya Baptista <spam_OUTABaptistaTakeThisOuTSE.EFACEC.PT> > To: .....PICLISTKILLspam@spam@MITVMA.MIT.EDU > Subject: Extending memory > Date: Tuesday, November 10, 1998 12:55 > > Hi all. > I think that I know the answer to this (_stupid_) question as I read the > datasheet: > is there any way (and I really mean ANY way) to extend program and data > memory on the 16F84? A few kilobytes extra would be extremely useful... > > Thanks, > AndrŽ Malafaya Baptista

Peter L. Peres wrote: > Seriously, if you want a large programming space investigate > interpreters of simple languages running on a PIC with program storage > in an external EEPROM or several. Actually, it's been done before. They called it the "BASIC STAMP". > Disadvantages: speed, code security, 3rd party programming tools or > high degree of experience required to make it work. > Advantages: too many to quote. I agree. It's a totally fascinating concept. Well worth re-inventing the wheel for (I mean you *could* go buy a BS-II but ...) and "rolling your own". -- Cheers, Paul B.

1. Data capacity can be easily extended with standard IIC ( I squared C) memories. Access is slower. Standard program memory can not be extended by "normal" means, but ... 2. You could interpret code stored in an external memory (along the lines of PIC STAMP BASIC) 3. Seeing you say you "really mean ANY" then I'll suggest the following. This obviously includes extra ICs This obviously allows extra cost So You could consider using a second PIC for key functions and communicate with it by passing parameters via a fastish serial transfer technique. Something (very) like SPI would take 3 or 4 pins and take a few 10's of cycles per byte transferred. Something like IIC or serial would take 2 pins and be potentially slower (but a pseudo synchronous version of standard async transfer could be quite fast). This may sound like a silly suggestion (it is :-)) but could be of serious use. I presume you are wanting to extend the 16F84's capacity due to its ease of reprogramming and internal EEROM. If so, you could develop suitable routines in the 16F84 and then, once operational, could put them in the "slave" processor and have them talk via the serial link. It need not be a 16F84. For this to be worthwhile the remote routines would have to be computationally complex enough to justify the slower access time. I'm actually doing something like this as an interim solution :-) A 16C71? sends A2D data to a 16F84 in async serial on one pin. Later on I'll change to a std serial A2D. Many "real world" examples exist. In their very old HX20 portable computer Epson had 2 x 6802 cpu's which communicated similarly - one looked after the "real time" data tape recorder control tasks. 4 New microchip products are (allegedly) coming with more flash rom Changing to another manufacturers product is, unfortunately, a highly tempting solution when you run out of 16F84 capacity. From: AndrŽ Malafaya Baptista <ABaptistaKILLspamSE.EFACEC.PT> is there any way (and I really mean ANY way) to extend program and da ta memory on the 16F84? A few kilobytes extra would be extremely useful...