- TMS370 Microcontroller/Gang Programmer User's Guide

Secondary Configuration Window—the Show Ranges Window
2-8
Operating in the Configuration Window
2.6.1 Selecting the Proper Program Algorithm
For EEPROM memory in devices, there are three programming modes:
writing 0s only, all 1s in the data bytes are ignored.
writing 1s only, all 0s in the data bytes are ignored.
writing 0s and 1s.
For all other types of memory,
writing 0s is the only programming mode.
The three modes provided for the TMS370 allow the selection of the most
efficient programming.
When the 1s and 0s mode is used, the programmer makes two passes through
the address range, programming the 1s in one pass and the 0s in the other
pass. Assume that the binary value 1010 1010 is to be programmed into a giv-
en address. First, the 1s are programmed, giving a value of
1x1x1x1x where
x is unknown (the previous contents of the location).
On the second pass, the 0s are programmed, resulting in
x0x0 x0x0 where x
is a don’t care state (in this case 1s from the first pass) so that the resulting
value after both passes is
1010 1010 , the desired value. This method is effec-
tive for modifying short segments of code.
If a large segment of code is to be modified, it will reduce programming time
by almost one half if you block erase to 1s and use the 0s-only mode.
When programming the EEPROM memory of TMS370 devices that also have
UV-erasable EPROMS, be sure to block erase the array before programming
the device. (Ultraviolet light causes the EEPROM bits to go to an intermediate
so that they must be block erased before programming.)