When i use external memory, port 0 and 2 will be used for data and addressing, so i'll be left with only the serial port and port 1. I open to suggestion on ways to add another two I/O ports. Thanks
You have many possibilities, my 3 favorites are: 1) Use a CPLD to implement memory-mapped I/O 2) Use the Philips PCF8574 which gives you up to 8 '51 type ports for 2 port pins 3) Use a WSI chipm which gives you some RAM, some ROM and some ports (2 1/2) Have fun, Erik Malund