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Topic: External SRAM Shield - XRAM (Read 452 times) previous topic - next topic

jlsilicon

Apr 27, 2018, 04:00 pm Last Edit: Apr 27, 2018, 04:13 pm by jlsilicon
Has anybody tried building an External SRAM Shield (XRAM) for the Arduino ?

I have used a few times the SPI SRAMs 23Lc1024 - but they are only 128Kx8
- This also had a R/W rate of about 100ksps

I had built XRAM boards of 32Kx8 and 512Kx8 - in the past for the Arduino (clk=16MHz).
- This used BitBanging - but R/W at about 2msps.
- This used 2 or 3 latches - and the pins came out to 12 or 13 pins - not great on the Arduino.

I was thinking about trying Bitbanging the 512Kx8 (628400) on the Arduino DUE (clk=84MHz) - without the Latches.
- I think the DUE uses 4 cycles per Pin IO speed - so PIO to R/W at 21MHz max (with clk=84MHz).
- Maybe use Page R/W scans like a SPI RAM/EE.
- This would give RAM R/W at about : 7msps - 10.5msps :
 => Rd  2 Cycles = Wrt AdrH Reg + WrtRegL                      + E + RE=1,  RE=0, Rd Dat8 = 21MHz / 2 = 10.5msps
 => Wrt 3 Cycles = Wrt AdrH Reg + WrtRegL + WrtDat8 + E + WE=1, WE=0                 = 21MHz / 3 = 7msps


- Has anybody tried this ?

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