I am anticipating the new PCBs coming in soon, (I have a tracking number but it doesn’t show up with Hong Kong Post or USPS). In light of this, I decided to do a little research on the SPI RAM so that when it gets here, I can quickly write code to test the functionality of the design. The SPI RAM I have chosen is a 23LC1024. A common manufacturer of this chip is MicroChip, I downloaded their datasheet for this chip and started looking at the process to write to and read from the RAM.
Notes for writing to SPI RAM:
Maximum 20 Mhz Clock for all data transfers (might cause me to slow down the FLASH)
Write speed only limited by clock speed.
Write command(0x02) followed by 24bit address followed by data
Page Mode 32bytes before sending a new address
Sequential mode can fill the whole RAM
Write is terminated by CS going inactive(HIGH)
Notes for reading from RAM
Same maximum clock speed.
read only limited by clock speed.
Read command(0x03) followed by 24bit address start receiving/clocking data from RAM
Three modes of operation, Byte, Page, and Sequential.
Byte mode only allows reading/writing one byte before having to resend an address.
Page mode all data is accessed in pages of thirty two bytes. Not very useful for this project.
Sequential mode allows access to all of RAM as one big block that I can start accessing from any point. I need to set the mode register bits 7 and 6 to 01.
I am going to start in standard SPI mode, Make sure it is working then adjust the code to start taking advantage of the SQI interface.