I'm a complete neophyte when it comes to hardware, so I'm sure I'm doing something completely stupid in the way I am trying to program a Freescale HC908QY4CPE.
I built the programming circuit shown in the manual and have tried downloading a program using the protocol documented in the manual. I have checked and rechecked connections, voltages, parts. The oscillator is oscillating, the bits from the serial line are getting to the right input, the 9V is getting to the IRQ line, and so forth. But the device sits there like a lump. I get the backtalk echo from the '125 hooked to the '232; I can see the security bytes and commands arrive at PTA0, I can see the 9.8304MHz on PTA5, the static voltages on the other pins are as per the manual; and I get no response at all from the ROM monitor. It has to be something I'm doing wrong as I've swapped the '908 with another with the same results.
I know I need to sacrifice a goat when I'm configuring a SCSI chain -- and DigiKey doesn't carry them! -- so what am I obviously forgetting here?
Thanks for any advice,
Brian Hetrick