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SBCv2 - SRAM_512K [message #1097]

Thu, 08 September 2016 05:07

trick-1 is currently offline

trick-1
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Registered: September 2016

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Hi Folks,

I am building up an SBCv2 Card and wanted to find out what component is used for the 512K SRAM. For the life of me I can't find a part number in the schematic, board pdf or part list beyond SRAM_512KO. If anyone knows what it is that would be greatly appreciated.

Thanks

Richard

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Re: SBCv2 - SRAM_512K [message #1099 is a reply to message #1097]

Thu, 08 September 2016 05:44

computerdoc is currently offline

computerdoc
Messages: 132
Registered: October 2015

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For the 512KB SRAM, I usually use the AS6C4008N-55PCN 4Mbit 512KB Static Ram chip. Here is the page on Digikey.com
< http://www.digikey.com/product-detail/en/alliance-memory-inc /AS6C4008-55PCN/1450-1027-ND/4234586>
On that page is a link to the datasheet.

Kip Koon
computerdoc at sc dot rr dot com
http://www.cocopedia.com/wiki/index.php/User:Computerdoc

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Re: SBCv2 - SRAM_512K [message #1102 is a reply to message #1099]

Thu, 08 September 2016 14:50

trick-1 is currently offline

trick-1
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thanks for that

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Re: SBCv2 - SRAM_512K [message #1103 is a reply to message #1102]

Thu, 08 September 2016 23:40

computerdoc is currently offline

computerdoc
Messages: 132
Registered: October 2015

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You are quite welcome trick-1.
I am beginning an SBC v2 build myself and I have been wondering what is the part numbers for the best, fastest version of the 16550, the 40-pin variety, and for the Z80. I have heard of the Z80A and Z80B. Is the Z80B the best one? Are there other variations on these parts that are better. I'd like to make this board the best, fastest, and most feature rich it is capable. Thank you in advance for your help.

Kip Koon
computerdoc at sc dot rr dot com
http://www.cocopedia.com/wiki/index.php/User:Computerdoc

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Re: SBCv2 - SRAM_512K [message #1104 is a reply to message #1103]

Fri, 09 September 2016 00:14

rhkoolstar is currently offline

rhkoolstar
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These are currently available, some more so than others ;-p

NMOS Z0840004 - 4 MHz
Z0840006 - 6.17 MHz
Z0840008 - 8 MHz

CMOS Z84C0006 - DC to 6.17 MHz
Z84C0008 - DC to 8 MHz
Z84C0010 - DC to 10 MHz
Z84C0020 - DC to 20 MHz

success RHK

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Re: SBCv2 - SRAM_512K [message #1105 is a reply to message #1104]

Fri, 09 September 2016 08:08

Andrew B is currently offline

Andrew B
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The parts list specifies a 4 Mhz oscillator for CPU_CLOCK - it's not clear to me if anyone has run the SBC_v2 faster than that.

This page on the wiki archive might be useful - Sergey mentions using an 8MHz CPU chip - https://retrobrewcomputers.org/n8vem-pbwiki-archive/0/358453 34/48860639/35845544/38298574/index.htm

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Re: SBCv2 - SRAM_512K [message #1106 is a reply to message #1104]

Fri, 09 September 2016 08:22

computerdoc is currently offline

computerdoc
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Thank you so very much for the part numbers RHK. I decided to order a couple Z84C0020 chips - one for the board and another for a spare. I always buy one extra chip especially when they are coming from so far away and when they are also new old stock. I really appreciate it.

Kip Koon
computerdoc at sc dot rr dot com
http://www.cocopedia.com/wiki/index.php/User:Computerdoc

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Re: SBCv2 - SRAM_512K [message #1107 is a reply to message #1105]

Fri, 09 September 2016 10:12

jcoffman is currently offline

jcoffman
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SBC v1 and v2 have both been run up to 12Mhz. I was unable to run at 16Mhz.
Both boards use 74LS-ttl exclusively.

82C55 should be the NEC "-2" version. UART, TL16C550-? used. ? = A or C.

The Alliance memory chip is the fastest, and cheapest. Less than $6; prices vary month to month.

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Re: SBCv2 - SRAM_512K [message #1109 is a reply to message #1107]

Sat, 10 September 2016 08:53

Jonas is currently offline

Jonas
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I run my SBC v2 at 20MHz. I have built it with ALS and F-logic and Intersil/Harris CP82C55A. Tested with PPISD and PropIO. I have not tested the board at higher freq than 12MHz with DiskIO v3, Dual SD or Dual IDE.

--Jonas

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Re: SBCv2 - SRAM_512K [message #1110 is a reply to message #1109]

Sat, 10 September 2016 09:03

Andrew B is currently offline

Andrew B
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Thanks for all the good info about speeds guys! Will make sure it ends up on the wiki eventually.

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Re: SBCv2 - SRAM_512K [message #1112 is a reply to message #1110]

Sun, 11 September 2016 22:42

briano is currently offline

briano
Messages: 18
Registered: November 2015

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If you are going to use the SBC V2 with a DiskIO v3 floppy controller board - you will need to run it at 8MHz minimum to make a 1.44Mb floppy drive work.

At 4MHz a 1.44Mb drive can only be made to work with 720kB floppy media (1.44Mb HD floppies have a higher data transfer rate that the Z80 can't keep up with at 4MHz).

This little nugget of information is buried deep in the old forum archives and threw me off for a few weeks until I found it.

I changed to a 8MHz crystal, but the z80A CPU struggled and was generally unreliable. Put in a 10MUz rated Z80 and it all ran nicely - 1.44Mb floppy now working correctly.

I stayed with the same LS chips I had already installed - no problems seen and it is a very stable system considering I was the one building it....

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Re: SBCv2 - SRAM_512K [message #1116 is a reply to message #1112]

Tue, 13 September 2016 15:11

etchedpixels is currently offline

etchedpixels
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Registered: October 2015

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1.44MB drive is 500Kbits/second or 64 clocks at 4MHz

With a sufficiently tight driver loop it can in theory be done (just about) if your FDC has a FIFO

B = 0, C = data register
HL = buffer

l1: in a,(FDC_ST) 11
add a 4
jr nc,l1 7/12
add a 4
jp p, error 10
ini 16
jp nz,l1 10

58 clocks

for 512 byte sectors you have to repeat the code block twice, not enough time to do another loop!

In theory it will work without a FIFO but I'm not sure you'll quite make the first data read fast enough after the status changes in all cases. The only way I know to do the status bit wait faster involves an MMIO address the byte after RAM. The RAM ends JP FF and the mmio causes it to jump to itself until an error or status change when it jumps to a different xxFF.

Alan

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Re: SBCv2 - SRAM_512K [message #1122 is a reply to message #1116]

Wed, 14 September 2016 04:53

briano is currently offline

briano
Messages: 18
Registered: November 2015

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Yes, no doubt it could be done on the SBC V2 at 4MHz.

For my case I was happy to use the existing rom floppy support so was simpler to change the crystal and run at 8MHz.

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Re: SBCv2 - SRAM_512K [message #1147 is a reply to message #1122]

Sat, 17 September 2016 06:22

computerdoc is currently offline

computerdoc
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Registered: October 2015

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I noticed that D2 is just labeled "Diode". Is this a small signal diode or an 1/8 watt rectifier diode?

Kip Koon
computerdoc at sc dot rr dot com
http://www.cocopedia.com/wiki/index.php/User:Computerdoc

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Re: SBCv2 - SRAM_512K [message #1154 is a reply to message #1147]

Sun, 18 September 2016 13:28

Jonas is currently offline

Jonas
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1N4148 or equivalent.

possible alt.
1N914
BAT43
1N5818

[Updated on: Sun, 18 September 2016 13:28]

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