The 16FDC design calls for lower density masked ROMs. As the higher density
ROMs got cheaper, cormemco switched over to using them. The pins that are
tied together are just unused address pins on the high density ROM. Things
1 make sure that the "start address" switches on the ZPU are set correctly
2 make sure that you are using the right DB25 connector (should be just a
through cable) and that the cable to your terminal is "right way around",
the TXD/RXD orientation of pins 2 and 3. I can never remember when you
DCE (Data Computer Equipment) or DTE (Data Terminal Equipment). You
only need TXD, RXD and ground (pin 7) between the computer and the
Try sticking a NULL modem converter in the path and see if that helps.
3 leave out everything except the ZPU, 16FDC and the 64KZ
4 be sure the 64KZ is set to bank 0 (zero)
5 check voltage levels on the bus
6 gently "rock" (ease out and reinsert) socketed chips, especially TI (Texas
Instruments) chips with tarnished pins.
> -----Original Message-----
> From: firstname.lastname@example.org
> [mailto:email@example.com]On Behalf Of B. Degnan
> Sent: Thursday, November 30, 2006 11:53 PM
> To: firstname.lastname@example.org
> Subject: RE: [midatlanticretro] Cromemco People in the Audience?
> Thanks. I had not checked the ZPU doc yet, getting to the RDOS ROM would
> be a start. Two of the pins on the RDOS are soldered together,
> unsure why,
> the picture I have on my site does not show this. I had tried to get
> anything to return on the terminal, but no result. It seems
> like power is
> OK, the system is in really nice shape. Almost like it broke
> down within a
> year or so and no one ever bothered to try to fix it. Hmmm.
> At 10:05 PM 11/30/2006 -0500, you wrote:
> >I use cromemco cards in one of my IMSAIs. The console serial
> >port is on the 16FDC. You want the 25 pin connector on it going
> >to a DB25 on the back. That will then attach to a terminal. The
> >machine will boot up into RDOS (the ROM on the 16FDC) if the
> >ZPU has its switch set to jump to C000 on start. The serial port
> >and the RDOS start up code will auto sync to whatever BAUD
> >rate your terminal is set to from 110-9600, you have to press return
> >a few times to get it to sync.
> Yahoo! Groups Links
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