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Hi Todd,
Great idea to use stronger solder for the SD mount! I wish I thought of that! I may just have to get the solder sucker out and do it right! J2 needs to be 74HCT245 if you are connecting to an original IMSAI FP board. I didn't spend any time researching why the 74LS245 chip didn't work. I just noticed the signals weren't getting through, so I tried the HCT, it worked, I moved on to the next task/problem. I hope you don't think less of me for such an approach. The whole design took many hours and many revisions to solve all the problems. Before doing this project, I thought the IMSAI front panel was a direct copy of the ALTAIR front panel, but now I know all the details. There is no doubt the IMSAI front panel was inspired and parts of it was a copy of the ALTAIR, but you can see that IMSAI made a few improvements in the design. There are two ways to kill the Shadow ROM. One is upon access to the SD Card, the other is via bit 0 of the output port. In the early version of firmware, I would copy the ROM (which contained the Monitor and CP/M BIOS) to upper RAM, then after the copy, the SD card is accessed, thus mapping out the ROM. The next instruction in RAM is a Jump to the Boot options (Monitor or CP/M). The latest version of firmware finds a HEX file on the SD card, loads it into RAM then puts two instructions in RAM and jumps to those instructions. Those instructions are the output that will turn off Shadow ROM and then jump to the file just loaded. It was done this way, so the HEX file that is loaded can be anywhere (except the top 1K). So to answer your question, this jumper changes depending if you are using early firmware or the latest firmware. Regards, Josh > Date: Sun, 1 Feb 2015 17:11:31 -0600 > From: litte...@mchsi.com > To: n8vem...@googlegroups.com > Subject: Re: [N8VEM-S100:6175] May I have a folder ? > > Josh. > > Yes, I soldered the side tabs for extra support, > even used silver bearing solder for extra strength. > > I spent the day filing sockets from my stores and > it looks like I need to order 1488's & 89's, a few > 8250's and a 74HTC245 (J2); unless I can sub a > 74ls245P ???? The Eprom is burnt and the SD card is > ready.... > > Question about Shadow Rom Kill (JP5) > > I figured 1-2 would be the setting to boot off > Eprom and jump to SD card to run the files, but > I noticed in your readme zip file you state; > > Jumper JP5 (Shadow ROM KILL) (above EPROM) must be set 2-3 > (upper position) and Output Chip 8212 (IC-J5) must be installed. > > I'm confused on this part. > > Todd > > > > ----- Original Message ----- > From: "Crusty OMO" <cru...@hotmail.com> > To: n8vem...@googlegroups.com > Sent: Sunday, February 1, 2015 9:44:06 AM GMT -06:00 US/Canada Central > Subject: RE: [N8VEM-S100:6169] May I have a folder ? > > > Todd, > > It looks good. I see you did the 2 jumpers from the back. Did you solder the SD card socket to the mounting pads on the left and right side of the socket? I usually like to put a large blob of solder there to hold the SD socket, I figure that's the only way it's being held in place. > > Remember, all electronic chips work because there's magical smoke inside them, the trick to keeping them working is to not let the smoke out. > > Cheers, Josh > > > > > Date: Sat, 31 Jan 2015 19:51:02 -0600 > > From: litte...@mchsi.com > > To: n8vem...@googlegroups.com > > Subject: Re: [N8VEM-S100:6165] May I have a folder ? > > > > Ok, so I gave it a try, Google it is. > > > > Here's my lame web site ;-) > > > > https://sites.google.com/site/litterbox99/ > > > > I'm almost done with the board. In the morning > > I'll plug it in with no IC's and verify the the > > various voltage regulators are doing their job > > and go forward.... > > > > Todd > > > > -- > > You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. > > To unsubscribe from this group and stop receiving emails from it, send an email to n8vem-s100+...@googlegroups.com. > > For more options, visit https://groups.google.com/d/optout. > > > -- > You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. > To unsubscribe from this group and stop receiving emails from it, send an email to n8vem-s100+...@googlegroups.com . > For more options, visit https://groups.google.com/d/optout . > > -- > You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. > To unsubscribe from this group and stop receiving emails from it, send an email to n8vem-s100+...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. |