intro, hyper7148

[Mike Pitts]

<<The C3 ecms at least have a card edge connector which allows access to
the processor bus and enough control to map out the on board ROM.>>

Unfortunately, one cannot easily alter the C3's onboard ROM. 
The thing I like about the P4 is that *all* of the microcode 
is located in the removable eprom. And there is ALOT of space 
to add functionality.  Also, the 68HC11 has a few more opcodes 
which make it a bit easier to program to than the 6801.  Not 
to mention that the F1 variety has onboard eeprom which GM 
didn't use, except for an ASCII ECM serial number.  This EE 
will be extrememly useful for on-the-fly tuning of the VE 
tables for my latest project.

<<as a monitor port for high speed monitoring. This has been done 
(the monitoring part) for the GN>>

DirectScan is a great tool!  I will probably get one in the future 
for help in tuning large injectors.

The P4 however does not require a DirectScan type of tool because 
the P4 has a "memory read" serial command that allows you to read 
any location in the 64k memory space, including registers and such.  
At 8192 baud, the speed has been sufficient for my purposes.  I've 
adapted the code in the eprom to accept a custom "memory write" 
command of my own design so that I can write to RAM and to EEPROM.  
I've even protected the routines from race-conditions.  I'd like 
to see someone do that on a C3 (if so, I'd buy it). 8-)

BTW: I have a friend who cooked his DirectScan by plugging the 
card edge connector upside-down (it's not keyed).  He's lucky he 
didn't cook his ECM, although they are plentiful and cheap in 
the local boneyards. 8-)

-Mike