Fast External Memory

[prstein]

Thanks Paul for your shared codes!!! It is great.
I did the same test, but used PIC16LF877(3.0V) and FM25V10(3.0V,1Mbit). I think the communication is the same, only with some minor modifications. I spent almost one day on it,still get no result yet.... Can you help me to check if there is anything wrong with it?
Thanks!

One Mbit? Now I have chip envy.

It looks like you need to add "FM_CS=1" right before the line "IF Disp = 1 THEN". The F-RAM never gets un-selected after the read.

It couldn't be that simple, could it? If that's not it please provide detail about what it is and is not doing correctly. If all else fails make sure it works using SHIFTIN and SHIFTOUT. If that fails as well use an o-scope to confirm ALL of the pins on the F-RAM are in their proper states.

Best Regards,
Paul

[hankshone]

One Mbit? Now I have chip envy.

It looks like you need to add "FM_CS=1" right before the line "IF Disp = 1 THEN". The F-RAM never gets un-selected after the read.

It couldn't be that simple, could it? If that's not it please provide detail about what it is and is not doing correctly. If all else fails make sure it works using SHIFTIN and SHIFTOUT. If that fails as well use an o-scope to confirm ALL of the pins on the F-RAM are in their proper states.

Best Regards,
Paul

Thanks Paul:-)
Really it is not quite easy. Last time it took me several days to find out the problem with SHIFTIN SHIFTOUT. I am sure the chip is working with those commands. But you know it is too slow... That's why I am switching to use the the hardware SPI to make it faster...
I will test it see what I can get..

[hankshone]

One Mbit? Now I have chip envy.

It looks like you need to add "FM_CS=1" right before the line "IF Disp = 1 THEN". The F-RAM never gets un-selected after the read.

It couldn't be that simple, could it? If that's not it please provide detail about what it is and is not doing correctly. If all else fails make sure it works using SHIFTIN and SHIFTOUT. If that fails as well use an o-scope to confirm ALL of the pins on the F-RAM are in their proper states.

Best Regards,
Paul

Still with no results... The reads I get for the four variables are all zeros. I mean X1 to X4.It seems like there are response from SDO. But never get anything in SDI from the os-scope. It is weird...

[languer]

This may help for HW SPI (From 877A datasheet):
"Any write to the SSPBUF register during transmission/reception of data will be ignored and the write collision detect bit, WCOL (SSPCON<7>), will be set. User software must clear the WCOL bit so that it can be determined if the following write(s) to the SSPBUF register completed successfully."

The following:

WriteSPI (read-modify-write):
WCOL=0
Rx_buff=SSPBUF ' CLEAR THE BUFFER
SSPIF=0 ' CLEAR THE INTERRUP FLAG
SSPBUF=tx_buff ' SEND THE BYTE
IF(wcol) THEN RETURN
WHILE(!SSPIF)
WEND
SSPIF=0;
RETURN

ReadSPI:
rx_buff=SSPBUF ' Clear the buffer
SSPIF=0 ' Clear the interrup flag
SSPBUF=0 ' Shift out a dummy byte What is this?
while(!sspif) ' wait for receive byte
wend
rx_buff=SSPBUF ' Get the byte
return

Can be changed to this:

WriteSPI (write-receive-read):
SSPIF=0 ' CLEAR THE INTERRUP FLAG
WCOL=0 ' CLEAR COLLISION BIT BEFORE WRITING TO SPI
SSPBUF=tx_buff ' SEND THE BYTE
WHILE(!SSPIF) ' WAIT FOR 8-BITS TO BE CLOCKED-OUT/CLOCKED-IN - THIS HAPPENS SIMULTANEOUSLY
WEND
Rx_buff=SSPBUF ' STORE RECEIVED DATA
SSPIF=0 ' CLEAR THE INTERRUP FLAG
RETURN

ReadSPI:
SSPIF=0 ' CLEAR THE INTERRUP FLAG
WCOL=0 ' CLEAR COLLISION BIT BEFORE WRITING TO SPI
SSPBUF=0 ' SEND/CLOCK-OUT DUMMY BYTE TO CLOCK-IN RECEIVED BYTE
WHILE(!SSPIF) ' WAIT FOR 8-BITS TO BE CLOCKED-OUT/CLOCKED-IN - THIS HAPPENS SIMULTANEOUSLY
WEND
Rx_buff=SSPBUF ' STORE RECEIVED DATA
SSPIF=0 ' CLEAR THE INTERRUP FLAG
return