9 Jan
2002
9 Jan
'02
8:03 a.m.
In a message dated 09/01/02 RCini(a)congressfinancial.com writes:
Hello, all:
Well, I'm picking up the 6502 SBC project that I started last year.
To reduce chip count I'd like to use Atmel PLDs for address decoding. I
downloaded some app notes from Atmel's web site but are there any practical
tips for using/programming these devices for use in a hobbyist project?
Rich
Hi Rich
I've used the MAX3000 series CPLD's, one problem I did find with these devices
is that the top mosfet in the output stage is an N channel device. If you
need to
drive logic with CMOS input levels you could run into difficulty. Pull-up
resistors
may be required. I couldn't drive logic level mosfets and some Analog Devices
parts with MAX3064 using 3V3 supply.
The 'byteblaster' parallel port JTAG programmer can be a bit erratic. I had to
decouple some of the JTAG signal lines with 47pF caps to make it work.
Atmel's free software is really easy to use once you get used to it.
Also, don't forget to tie un-used input pins to ground or Vcc.
Because I was never happy with Atmel's MAX3000 output stage I switched
over to using Xilinx Coolrunner. The Xilinx parts have a true complimentary
output stage and you get proper rail to rail drive levels, they're also lower
power too.
On the downside, you have to buy a Xilinx JTAG programmer and their
software leaves a great deal to be desired.
Good luck
Chris