Date   : Tue, 20 Oct 2009 15:53:43 +0100
From   : michael.firth@... (michael.firth@...)
Subject: SRAM on the BBC+ 64K

> -----Original Message-----
> From: 
> bbc-micro-bounces+michael.firth=bt.com@... 
> [mailto:bbc-micro-bounces+michael.firth=bt.com@...
> .uk] On Behalf Of wookie
> Sent: 20 October 2009 12:15
> To: bbc-micro@...
> Subject: [BBC-Micro] SRAM on the BBC+ 64K
> 
> Hi
> 
> Following on from the discussion on cheap ROM upgrades for 
> the beeb, I 
> was wondering, since to BBC+ can take 32K ROMS/EPROMS can I 
> stick a 32K 
> SRAM chip in there and hook up the extra leads needed to make 
> it work as 
> sideways RAM ?
> 
> What spec of SRAM would I need, i've found the following in a 28 pin 
> package, will it work ?
> 
> Part Number = KM62256ALP10
> Manufacturer Name = Samsung Semiconductor
> Description = General-Purpose Static RAM
> Number of Words = 32k
> Bits Per Word = 8
> t(acc) Max. (S) = 100n
> tW Min (S) = 100n
> Output Config = 3-State
> P(D) Max.(W) Power Dissipation = 1
> Nom. Supp (V) = 5
> Package = DIP
> Pins = 28
> Technology = CMOS
> 
> As far as I can tell the pinout is correct...
> 
> A14-1  28-Vcc
> A12-2  27-NOT WE
>   A7-3  26-A13
>   A6-4  25-A8
>   A5-5  24-A9
>   A4-6  23-A11
>   A3-7  22-NOT OE
>   A2-8  21-A10
>   A1-9  20-NOT CS
>   A0-10 19-D7
>   D0-11 18-D6
>   D1-12 17-D5
>   D2-13 16-D4
> Vss-14 15-D3
> 
That should be fine, you'll just need to hook pin 27 up to a write enable
signal (I would suggest pin 24 of the 7002 ADC chip), and pin 1 to a source
of the ROMSEL LSB (the link bank to the left of the ROMs is the easy source)

Have a look at:

http://www.firths.org/bbc/my_b+128k.html

For my example of installing a lot of SRAM into a B+

Regards

Michael