3 - 16k binaries on an 27C512 Eprom.
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From: DMackey828 on 31 Jul 2010 18:07 I am trying to make a 3 Kernel ROM adapter for the 64C. It requires a 27C512 eprom because each part is 16k in size, (Basic 8k/Kernel 8k) 49512bytes in size total. I pad the low end of the eprom 0000-3FFF with 0's because it will not be used. because the binary must be 65536bytes in size to completely fill the eprom. One thing I did find out was that Pin 1 (A15) must be Open Circuit which is NOT show in that pic but is shown on the LEFT side. The adapter I am trying to use is : http://www.spacetaxi.bravehost.com/ELECTRON/EPROM-3W-SW.htm The one on the RIGHT. The page loads real slow for some reason. It says something about "A wire from Pin 13 & 14 to Switch-to (GND) If I short out pins 13 (O2) and 14 (GND), the computer won't do anything. I can get the border & background to change the proper colors BUT no Text is displayed. I tested each 16k section using a 27c128-16k eprom, all three section of the 64k binary work PERFECT by themselves. Any idea what I'm doing wrong? This SHOULD work, I can's see any reason why it wouldn't. TIA
From: Sam on 31 Jul 2010 20:08 Hello Don, I've modified the schematic from the link in your message. You can find it here: http://www.siemappelman.nl/kernal.jpg You need a three-way switch or toggle switch with a free middle position. A14 and A15 are high now on "my" schematic. In this situation Bank 4 is selected. In position 3 A14 is high and A15 is low and Bank 3 is selected then. In position 1 A14 is low and A15 is high and Bank 2 is selected then. When you make A14 and A15 low Bank 1 is selected but you don't use that. Regards, SAM
From: Sam on 31 Jul 2010 20:20 Hello Don, I've modified the schematic from the link in your message. The text is completely wrong and must be: A wire from pin 14 (GND) tot switch. Two 4,7 K resistors from pin 28 (VCC) to pin 27 (A14) and 1 (A15) A wire from pin 27 (A14) and pin 1 (A15) to switch You can find it here: http://www.siemappelman.nl/kernal.jpg You need a three-way switch or toggle switch with a free middle position. A14 and A15 are high now on "my" schematic. In this situation Bank 4 is selected. In position 3 A14 is high and A15 is low and Bank 3 is selected then. In position 1 A14 is low and A15 is high and Bank 2 is selected then. When you make A14 and A15 low Bank 1 is selected but you don't use that. Regards, SAM
From: Jim Brain on 31 Jul 2010 22:48 On 7/31/2010 7:20 PM, Sam wrote: > Hello Don, > > I've modified the schematic from the link in your message. > The text is completely wrong and must be: > > A wire from pin 14 (GND) tot switch. > Two 4,7 K resistors from pin 28 (VCC) to pin 27 (A14) and 1 (A15) > A wire from pin 27 (A14) and pin 1 (A15) to switch > > You can find it here: http://www.siemappelman.nl/kernal.jpg > > You need a three-way switch or toggle switch with a free middle > position. > > A14 and A15 are high now on "my" schematic. In this situation Bank 4 > is selected. > In position 3 A14 is high and A15 is low and Bank 3 is selected then. > In position 1 A14 is low and A15 is high and Bank 2 is selected then. > When you make A14 and A15 low Bank 1 is selected but you don't use > that. > > > Regards, SAM I agree the text is wrong (they meant A13 and A14, but even that is wrong, it should be A14 and A15. Clearly the text is from the 8K mapping). But, I fail to see, Sam, how your new schematic is different from the original in the first link? Both tie A14 and A15 high via 4.7K resistors, and tie those two lines to a STDT (ON-OFF-ON) switch, with the center as ground. Am I missing something? Jim
From: Clocky on 1 Aug 2010 03:07
DMackey828 wrote: > I am trying to make a 3 Kernel ROM adapter for the 64C. It requires a > 27C512 eprom because each part is 16k in size, (Basic 8k/Kernel 8k) > 49512bytes in size total. I pad the low end of the eprom 0000-3FFF > with 0's because it will not be used. because the binary must be > 65536bytes in size to completely fill the eprom. One thing I did find > out was that Pin 1 (A15) must be Open Circuit which is NOT show in > that pic but is shown on the LEFT side. > > The adapter I am trying to use is : > > http://www.spacetaxi.bravehost.com/ELECTRON/EPROM-3W-SW.htm > > The one on the RIGHT. The page loads real slow for some reason. > > It says something about "A wire from Pin 13 & 14 to Switch-to (GND) If > I short out pins 13 (O2) and 14 (GND), the computer won't do anything. > > I can get the border & background to change the proper colors BUT no > Text is displayed. I tested each 16k section using a 27c128-16k eprom, > all three section of the 64k binary work PERFECT by themselves. > > Any idea what I'm doing wrong? This SHOULD work, I can's see any > reason why it wouldn't. > > TIA What you need to do is connect A14 and A15 to +5V (VCC pin 28) through a 4.7K resistor (anything from 2.2 to 4.7K is fine actually) and then connect A14 and A15 to each side of a three position switch with the centre pole going to GND (pin 14) so that toggling the switch will alternately switch A14 and A15 to ground. |