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Re: N8-4314 Issues

To: n8vem@googlegroups.com
Subject: Re: N8-4314 Issues
From: Wayne Warthen «wwar…@gmail.com»
Date: Tue, 23 Jun 2015 15:20:05 -0700 (PDT)
In-reply-to: <ddd71163-b65b-4852-845b-524d7c17d646@googlegroups.com>
References: 74c7c260-c487-4de0-9d4e-8fa91356ec4f@googlegroups.com 1218c8a3-442a-451b-b9ba-10f034cf4ab9@googlegroups.com <ddd71163-b65b-4852-845b-524d7c17d646@googlegroups.com>

Hi Rich,

A few comments below…

–Wayne

On Saturday, June 13, 2015 at 8:39:14 AM UTC-7, RichLeary wrote: <blockquote> Great News - my second attempt at building a N8-4314 appears to be a good one. System booted right up using ROMWBW 2.7.1 and is totally stable. SD card and LED are working as expected. RTC is working correctly.

</blockquote>

Glad it the RTC is working on this one.

I need to test floppy interface and just for fun exercise some of the other I/O including the video, PS2 keyboard, and audio. I need to do some research on that score. As is, the 9918 appears to be responding to some ROMWBW initialization as the screen shows a full screen of the same symbol after a reset. The usual lights on a connected keyboard are dark - do not know if that means anything.

</blockquote>

RomWBW initializes the screen to blanks. If you see a screen full of some character, that does imply the video chip is working, but also implies that the system is running too fast for the video chip. You can probably resolve this by increasing the I/O wait states in the RomWBW config file when you create a custom ROM.

A note on as-built configuration. I used all 74LS logic except for the 574's that are 74ALS574's just because I did not immediately find 74LS574's at DigiKey, my preferred source. CPU oscillator is 18.432 MHz. Since I have no plans to use the ECB interface I have not set the K1 configuration - there is no jumper on K1. K21 & K22 are set to 1-2 jumpered but the two 4700 ohm resistors are still in place - without anything connected to the ECB bus this should also be a “don't care”.

Rich Leary

</blockquote>

References:
- Re: N8-4314 Issues
  - From: RichLeary <Richar…@gmail.com>

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