SPI Write Buffer Timing

[Suraj143]

Want to know the time takes (Cycles) after loading the 1st SSP1BUF to the next SSP1BUF.....

Thanks

            ;SPI Clock = 1.5uS (Period)
                          ;Instruction Cycle = 250nS
              
                movwf     SSP1BUF         ;Previous Write to SPI
                ;
                ;From Here Needs the timing to next SSP1BUF
                ;
                movf     INDF0,W
                call     Table_2
                movlb     .0                 ;switch to Bank0
                btfss     PIR1,SSP1IF     ;Has the byte been sent
                goto     $-1             ;No
                bcf     PIR1,SSP1IF
                movlb     .4                 ;switch to Bank4
                movwf     SSP1BUF         ;Time ??             
              
Table_2         addwf    PCL,F
                retlw    00h
                retlw    .1
                retlw    .10
                retlw    .8
                retlw    .16
                retlw    .53
                retlw    .2

 

[Ian Rogers]

It will be the eight clock cycles... But multiply by which ever FOSC /? you have used in the SSPCON1 register.. Most of us just poll the SSPIF flag, that tells you when its done. ( clear it first before filling SSPBUF..)

edit** I see you have done that!!

 

[Suraj143]

Ok. For example for 8 bits if it takes 12uS time I have to wait 12uS time after I load it to SSPIBUF? In other words I have to poll until 12uS time?

 

[Ian Rogers]

Ok. For example for 8 bits if it takes 12uS time I have to wait 12uS time after I load it to SSPIBUF? In other words I have to poll until 12uS time?

no.. just wait for the flag.. You're code snippet has this already..

 

[Suraj143]

Ya I know I have to wait until Flag Occurs.What I mean was the flag will occur after 12uS time after I loaded to SSP1BUF!!

 

[Ian Rogers]

what have you set SSPCON1 to.. FOSC / what?

The way you have it is :-

Is the last byte gone?
Yes. Send next one
No. wait a bit

I do it the other way round as I want what has come:-

clear flag
Put byte in buff
wait for flag
return whats come back...

Then you get full duplex..