Re: LZ: Possibility of RAM Expansion
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Re: LZ: Possibility of RAM Expansion
On Mon, 9 Sep 1996 21:23:23 -0700 (PDT), you wrote:
>I was quite intrigued by Ed Plese's and Per Finander's use of the I2C =
bus (
>A data bus format that can operate multiple IC's on a 2-wire bus ) to =
run
>the temperature sensor and other I2C-compatible circuits.
>
>While ordering the sample temperature chip from National Semiconductor (
>www.national.com ) to build Ed's temperature sensor, I also happened to =
find
>an available sample for a I2C-compatible EEPROM chip. I'm personally =
going
>to try creating a plug-in memory bank through the link port by using
>Finander's I2C routines.
>
>The chip, in specific, is a NM24C17L 16K-Bit Serial EEPROM with Write
>Protect and I2C Synchronous 2-Wire Bus support. However, each bus can =
only
>address a maximum of 16K bits, the size of one chip. If I could do =
multiple
>buses using digital or DC switches, that might work... but I'm not sure.
>
>If anyone with more experience in I2C ( Finander? ) could help me, this
>would be a great step in the right direction. I personally think that =
using
>either EEPROM bays with I2C or recording modulated audio is the way to =
go.
>The catch with audio, though, is both finding a way to record this =
without
>change from player to player, and the writing of such a program.
>
Well, I think you can all stop talking about the I2C and Tape Backup
memory expansion methods. I've come up with a Ram Expander circuit
with the following characteristics:
--Easy to build with cheap/easy to find components
--Relatively high speed transferrs (at least 400-1000 bytes per
second)
--Extremely high capacity (up to 8 megabytes!!!)
--Can be made on a 6" x 4" board
--Have battery life of 10-30 hours.
Sound too good to be true? Well, I think I've done it. Please note
that the expander is in its Beta version (that is, I haven't built it
yet but it will be done really soon). The actual circuit I'm
proposing uses a 512k x 8 Dallas Semicondoctor NV-SRAM, but smaller
densities (e.g. 32k or 128k) can be substituted without circuit
modification.
The unit DOES NOT use a microcontroller, it merely uses standard
74LSxx parts which makes (by far) the majority of the cost a function
of the memory chip you choose. The circuit also contains provisions
for 2 8 bit I/O ports for addition of simultaneous external keyboards/
LCD's/ or even parallel port devices (such as printers).
I"ll be releasing the entire schematic/text file as soon as I'm done
writing the circuit discriptions (that should be later tonight,
9/10/96).
It's been a long time since I've been on the list (in case you're
wondering, I'll probaly never come out with a newer version of
Columns), so if anyone feels I should know anything that's come up
before, let me know.
References: