FAQ list updated 6 May 2001, By S.G.Willis Listed bellow are the answers to some of your questions. How do I go about developing some pic84 code ---------------------------------------------- Q1. What is involved in developing and programming a pic84 ? A1. Follow these steps, 1) Have a look at my demo file (PPTEST.ASM). Then write your assembler file using DOS edit or PFE (programmers file editor) for windows etc. Make sure this line is included in your file, LIST P=PIC16C84, F=INHX8M 2) Assemble the file :- MPASM FILE.ASM you can get a copy of the assembler from my site 3) Then programme the pic using ICPROG you must set the hardware as shown on my page also make sure the fuse settings are correct PIC508/509 OSCCAL value ----------------------- Q2. I am using your software pp875 and the hardware with an UV-erasable PIC12c509. If you erase these chips, you loose the calibration word, which Microchip programs at address $3FF ? A2. Read the value out before erasing the chip, and then place it within your program code eg:- ORG 0x3FF DW Don't forget to remove it when using a OTP device ! Message: OSCCAL value already programmed ---------------------------------------- Q3.Why do I get "Message: OSCCAL value already programmed" ? A3. When you are programming a OTP 508/509 the OSCCAL (internal RC calibration value) is already programmed into 0x1FF (508) or 0x3FF (509) by Microchip. Make sure your code does not over write this value. If you get this message with an eprom device it's because the chip has not been erased properly. Flash PICS ---------- Q4. I am currently using pic 16C84-04 but find this part is now only supplied as a FLASH ROM device (pic 16F84-04) instead of EEprom. Do you know if modifications are required to the parallel port programmer to use this pic ? A4. I have down loaded the latest PIC16C84 and PIC16F84 programming specs from microchip and at first glance they are very similar. A few timing changes have been made, but nothing drastic. The configuration word now has more 'code protect' features. Programming I2C EEPROMS ----------------------- Q5. I'm wondering if your programmer supports I2C (24C0x) chips? A5. Yes with a simple adapter it is possible to program most I2C EEPROMS using IC-Prog. Connect the 8 pin EEPROM socket to the 18pin or ISP sockets as follows, 8pin 18pin ISP 1 5 GND 2 5 GND 3 5 GND 4 5 GND 5 13 RB7 6 12 RB6 7 --- --- 8 14 VCC Protecting PIC12C508/9 ---------------------- Q6. Why can I still read my 508 when the protect flag has been set ? A6. The protection flag on the 508/9 only stops ROM addresses > 0x3F from being read (zero). Any data in address range 0-0x3F will read as normal Getting the transistors ----------------------- Q7. I have some problems to get the transistor ZTX 500 ! Do you know some compatible transistors ??? A7. It's a PNP general purpose device (HFE 100, IC 100mA) so anything that fits should be ok. Try a BC557, BC558, BC640 or 2N3906. Note the BC557, BC558, BC640 must be rotated by 180 degress to get the correct pinout. Multiple pic - parallel programming ----------------------------------- Q8. Can I plug several pics ontop of each other and programme them all at the same time - in parallel. A8. No you can't programme more than one pic at a time, for many reasons, The increased power supply current will overload the programmer. When the programmer verifies the pics it will not be able to verify the pics individually - major confusion. etc... I can't write any PIC12c508 chips --------------------------------- Q9. I cant write any PIC12c508 chips. A9. I always try a PIC16C84 first to test out the hardware. If this is ok but the 508 still won't work check the two 1nF filter caps are correct on the port pins D0/1 and VPP is 13V. Also check the 508 has been fully erased I find they take a bit longer than other PIC's. That's it !!!! Steve...