Hello All,

Background:
I have a recently constructed a prototype PCB for a 18F452 in the TQFP
pacage.
I have an old ITU Technologies programmer model PIC-1a (TAIT compatible).
I am using ICPROG version 1.05C.
The date code on my 18F452 is 04252JG. The date code on the 18F252 that
worked is 02124GP (see below).
There are no parts populated on the board other than the PIC, ICSP header,
and a 0.1 uF decoupling cap between VSS and VDD.

Problem:
I am continually getting verify errors (at address 0 or 1) when attempting
to program. When I read out the program and data memory, only the first 
few
nibbles have changed. The values that they change to seem to be random.

I have also noticed that when programming zeros into program memory the
programming works properly, but as soon as a non-zero value is encountered
the location fails verify and subsequent locations seem "untouched".

Note:
I did forget to ground the PGM/RB5 port the first time attempted to 
program
the PIC.

Debugging Steps:
I have performed continiuity checks between the ICSP header and the pins 
on
the PIC as well as cross-continuity checks with no errors discovered.
I have verified the programmer/software using an old 16C84 and a new 
18F252
on a breadboard with no errors.
I have checked the output voltages from the programmer (0V and 5V within
0.25V on VCC, CLK, and DATA). VPP is at right about 12.75V.
I have also tried several programming speeds (IO Delay paramater in 
ICPROG)
including the minimum and maximum.
The clock pulses during programming are 15 us wide (30 us period). This
timing worked with the 16C84 and the 18F252.
I have tried 2 new 18F452 on new boards with no change in results.

Question:
Has anyone experienced problems like these before? What were the 
solutions?

Could applying the high programming voltage while leaving PGM floating
damage the chip?

Thanks in advance,

Adrian Hill
_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist