Hi there, I'm interested in something similar ! I too am about to start my first serious pic project and I intend to have serial i/o to pc, 16 digital inputs, 9 relay driver outputs an lcd display and up to 8k of EEPROM (on serial i2c bus). I plan to use a pic16c74 with 9 outputs dedicated to a uln2803 relay buffer. 8 pins multiplexed as one of 2 8bit banks of digital inputs ( reading from an 8 bit tristate latch ) and also drive 8 of the data lines on a hitachi lcd display. With the other 3 control lines provided by dedicated pins. A further 3 pins are allocated to the multiplexing of the 3 devices ( A little overkill but not too much) . Personally I have a preference to EEPROM on an I2C bus as this only uses 2-3 wires and doesn't waste much board space or need complex wiring.. As for the serial I/O. Well the 16c74 has its own serial port but you may need a max232 to to convert its ttl outputs to the 12v rs232 standard. However if these are you only needs then you may be more inclinded towards using a pic16c84.. As this chip has an onboard eeprom 1k for program storage. It is a much more project development friendly device. If your program will fit in 1K and then data speeds are slow enough to store in an EEPROM. ( serial rates probably would be ). Also this chip is considerably cheaper than its larger counterpart. $12 as opposed to $50 for the 16c74 EPROM ver. Irish Prices !) However if I remember correctly the 16c84 may not have an inbuilt UART ( Only just realised that ) so you may have to code this youself. (Tricky I recon) Perhaps the 16c71 may be a happy compromise.. Anyway as you probably realised I am not the most experienced in programing PICs but perhaps my suggestions may fuel comments from other more experienced PICers. Anyway best of luck in your endevours and let me know how you get on, as I will probably experience similar problems. David Nicholls On Fri, 6 Dec 1996, Alex I. Torres wrote: > Hi All PICers ! > > Wednesday December 04 1996 11:12, > Ralf.Sigmund@STUD.UNI-HANNOVER.DE wrote in PICLIST: > > RS> I am about to start my first Pic Project. It is a small > RS> device that should > RS> > RS> (1) accept digital data (numbers & strings) from a > RS> Measurement device via RS 232 at any time. > > You only receive data from this device ? (1) > > RS> (2A) store the Information in memory (approx. 20 Kilobytes > RS> of data) > > It is the most problem. If you use 16C74 you can put one port as > DATA (8 bit), other ports as ADDRESS (15 bit for 32 kB) > and -CS,-WR,-OE (3 bit) : 8+15+3=26 bit. C74 have 33 bit I/O. > What about using 3x 6264 (8kx8 cmos static ram) or other with > more memory space (62256) ? (I have many 6264 :-) > 13 bit for address, and 3 bit for chip selection. > > RS> (2B) display the latest aquired data on a LCD display > > If you want to built low-cost device try to use any 4-digit LCD > display with Microchip's AY-0438 controller. It require onle 3 > wire (PIC's I/O) for communicate. > > RS> (3) send all data to a PC via a second RS 232 > > Only send ? (2) > > RS> After reading some FAQs there remain still some questions: > RS> > RS> What kind of Memory should I use (lithium battery backed up > RS> static ram, EEPROM, Flash...)? How do I wire the memory to a > RS> PIC? Any Circuits ? > RS> > RS> How do I wire two RS 232 ports ( one with Hardware Handshake > RS> )? > > If (1) and (2) is true the best way is 16C74 that have serial port. > > RS> Do I need a UART or is just a simple MAX 232 signal > RS> converter enough? > > It's depend for the RS232 speed. If you not use high speed the > simplest (and low cost) solution is : > +5v --------------| e > | / > from PIC's TxD R2 |/ > --->----- R1----|----|\ c > | \---------------------->--- RS232 RxD > | > | > R3 |\ | > |----------| /|-------<--- RS232 TxD > _|_ |/ | | > ---+C1 | R1,R2,R3 2-10 kOhm > | | C1 5-100 uFx16-20v > _|_ | > to PIC's RxD | > ----------------<------------------------------ > > I dont remember, mayby PIC's signals must be inverted. > > Resume: > using 16C74 with 3x 6264 and AY-0438 : > 8data+13address+3xCS+OE+WE+2xRS232+3xAY =31 bit. > You have 2 I/O free for handshake. > --------------------------------------------------------------------- > Best Wishes, Alex Torres. > Kharkov, Ukraine, exUSSR. > E-Mail To : altor@cook.kharkov.ua via InterNet > or 2:461/28 via FidoNet > > --- GoldED 2.50.A0531+ >