In SX Microcontrollers, SX/B Compiler and SX-Key Tool, kmonsx wrote:

Hi,
 

I'm going to be using some Ramtron serial fram with my SX28.  I've never used any type of external memory, but I've read the datasheet carefully.  It looks pretty straight forward.  The datasheet was a pretty easy read, and for someone with limited exposure to this stuff, that's saying something.

 

Are there particular gotchas or things to look out for?  I'll be bit-banging the various leads(CS, SCK, SI/SO, and HOLD) and won't be using interrupts to talk to it.  My ISR is busy with some other tasks, and although I could combine them, it might get ugly.

 

I plan on writing to it at approximately 7.14 mhz, using an asymmetrical clock.  I think my HIGH time is 100ns, and my low time is 40ns.  Anyone see any trouble doing this?  These numbers, and the speed comes as a direct result of the number of instructions required to manipulate the leads.  The write routine, which is the only time-sensitive routine for me, is basically just shifting a byte out, bit by bit using RL, copying C to the port(it's MSB), incrementing a counter, checking to see if I've shifted 8 times, and then looping back.

 

I plan on setting the chip up first(CS), doing a WREN and a WRITE with the appropriate address, and then putting the chip on HOLD and then just clocking in new data so I keep my successive writes short and sweet.

 

Any advice, even generic advice regarding serial memory, would be appreciated.

 

Thanks.

 

Keith

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