Re: [N8VEM: 18409] Mark IV Troubleshooting

[John Coffman]

Anthony, I would assume that TEST1B came from the updated zip file. LED should be green during RESET.  Good. Do you have experience wiring RS-232 communications cables?  The output from the Mark IV board, like the SBC v1/v2, looks like a terminal.  Hence, to connect to a terminal you must cross lines through a null modem. Check the Serial Interface tutorial; it applies to all boards: http://n8vem-sbc.pbworks.com/w/page/44302435/Serial%20Interface%20tutorial Make sure the TXD from the Mark IV is connected to the RXD of your PC or Terminal.  Electrically, see if the output is toggling as characters are transmitted.  Trace back through the MAX233 to be sure the TTL level output from the Z180 is transmitting, too. Q:  Are you running the board standalone, or plugged into a backplane?  You said you had checked the Vcc voltages across the board. --John On 07/09/2014 06:18 PM, Anthony DeStefano wrote: I've been banging my head for about 3 days now trying to get a Mark IV to run the TEST1B.BIN successfully. So far I can verify the following: 1. I'm using a Z8S18033 with a 18.432 oscillator and have a good clock on pin 3 and 1/2 on PHI pin 68. 2. The power LED goes green and stays green. 3. I checked all sockets for voltage and ground and all are okay. Nothing it getting hot to indicate a true short 4. Reset seems to be working correctly. At least I see it drop on pin 1 of U31. 5. ROM is a SST39SF040 flash programmed with the minipro programmer. P11 and P12 are in the 2-3 position for flash. 6. I'm using SN74LS for all the logic chips. Like many on the list this is my first major digital electronics project. I do have access to a scope and a Salaea 16 port logic probe. Poking around I see various things twiddle, but I'm not sure where to look for the fault. I've thought about trying a slower oscillator, but would need to order one. Any help would be appreciated. -- You received this message because you are subscribed to the Google Groups "N8VEM" group. To unsubscribe from this group and stop receiving emails from it, send an email to n8vem+unsubscr...@googlegroups.com. To post to this group, send email to n8vem@googlegroups.com. Visit this group at http://groups.google.com/group/n8vem. For more options, visit https://groups.google.com/d/optout.