NUE-PSK Digital Modem

HC908 Programmer

Simple programmer circuit used to program the modem's U5 Keyboard Controller



A very good friend (Bob, K7HBG) in the Micro908 Antenna Analyzer forum took the time to build up and verify a programming circuit for the HC908 processor, as recommended by Motorola/Freescale in their HC908 data manual.  When connected to your PC via the RS-232 serial port, and running the WinIDE development environment from P&E Micro (standard for programming the HC908 chips), you can program the HC908 chip used in the Micro908 Antenna Analyzer and in the NUE-PSK modem


Here are Bob's notes and schematic ... thanks Bob!


Hi George,
Here is the programmer I built. There are bunches of variations of this design on the Internet. The only claim that I make is that it works just fine to program the Plug Board. A few notes are in order at this time;


1) My schematic shows more parts than are needed to program the 908AB. I thought I'd get a bit fancy and add oscillator modules and a little switch for applying +5 and ground to selected pins of the device for programming purposes. These parts are NOT needed.

2) reference the HC908AB Manual found on the Freescale web site and take a look at Section-10, Pages 159 for programmer hookup and 160 for pin jumper options.

3) The HC908 Plug Board manual that George presents on the AMQRP web site shows an exerciser board he created and a programming socket hook up.

4) My programmer schematic shows the typical pinout and signal connections for the standard "MON08" interface plug. This was for my reference only and not needed.

5) The onboard 4 MHz crystal is used while programming and so, outboard oscillator U3 and U4 are not used.

6) The signal I show as "IRQ(Vpp) is actually the official "Vtst" 8V programming signal.

7) The "RST" signal is not needed.

Any questions? PLEASE ask!

73's Bob  "k7hbg .... at ... dslextreme ... dot... com"




Page last updated:  June 19, 2008