'ppzsum' is a program to convert between various hex formats used by EPROM programmers and related embedded-systems software tools. As a side-effect, it also generates a checksum which will match that reported by a Stag PPZ, PP39, or PP42 EPROM programmer.
The Stag PPZ EPROM programmer was a 6809-based system with built-in CRT display and pluggable programming modules. The PP39 was a smaller unit with a 14-segment VFD. The PP42 is slightly bigger and newer than the PP39, but has the same VFD and membrane keyboard.
The default input format to 'ppzsum' is binary. This is a popular format for ROM images on the Internet, but is rarely used by EPROM programmers because it is difficult to transfer reliably over a serial (RS-232) connection.
EPROM programmers generally use either Intel hex format, Motorola S-Records, or MOS Technology hex format. 'ppzsum' can generate all of these.
The checksum is simply the 16-bit sum of all the bytes contained in the hex file (after decoding), expressed in hex. It is a very weak checksum, suitable only for detection of transmission or programming errors. It is not in any way secure against malicious alteration.
