LE>> Surface-mount SOIC or QFP device which is NOT programmable
LE>> in-circuit and requires removal, EXTERNAL programming, and
LE>> resoldering. Hardware damage.
JO> I'm curious how the non-programmable device got wiped in the first
JO> place, if the write voltage isn't present?
Let me rephrase that... sorry, it was ambiguous. This is an EEPROM (not 
EPROM) which can only be programmed in situ /by the host uC/ because it's not 
isolated from the address and data buss of the machine and there's no way to 
get all the other devices on the busses to go into a high-impedance state.
The normal algorithm for this for a modem is :
 * terminal sends "start erasure" sequence (differs from modem to modem, but
   there is a standard Rockwell command which MANY modems support).
 * modem microcontroller copies the erase-and-program algorithm to buffer RAM
   and jumps to the RAM copy
 * EEPROM is erased and erasure verified using the RAM copy of the firmware
 * modem sends "ready for new image" code to terminal
 * terminal uploads new firmware image and modem microcontroller programs 
   EEPROM
 * uC performs CRC check
If the process is interrupted after the erasure sequence starts, then the 
modem is in a DANGEROUS state. If the user doesn't recognize what has 
happened, and turns the modem off, the RAM copy of the code is lost, and the 
device is (to use a technical term) screwed. If the EEPROM was socketed, the 
user could fit a replacement mailed from tech support. As we were discussing 
wave-soldered surface-mount devices... no such replacement is possible. The 
modem requires removal and replacement of the EEPROM.
(Bootblock EEPROMs get around the problem, yes, but not all devices use them. 
Modems in particular).
-- Lewin A.R.W. Edwards [Team OS/2]  Tel 0412809805 * http://www.zws.com/
--- MsgedSQ/2 3.35
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