Datasheet

PIC18F46J11 FAMILY
DS39932D-page 290  2011 Microchip Technology Inc.
;Somewhere else in our project, lets assume we have
;allocated some RAM for use as SPI receive and
;transmit buffers.
; udata 0x500
;DestBuf res 0x200 ;Let’s reserve 0x500-0x6FF for use as our SPI
; ;receive data buffer in this example
;SrcBuf res 0x200 ;Lets reserve 0x700-0x8FF for use as our SPI
; ;transmit data buffer in this example
PrepareTransfer:
movlw HIGH(DestBuf) ;Get high byte of DestBuf address (0x05)
movwf RXADDRH ;Load upper four bits of the RXADDR register
movlw LOW(DestBuf) ;Get low byte of the DestBuf address (0x00)
movwf RXADDRL ;Load lower eight bits of the RXADDR register
movlw HIGH(SrcBuf) ;Get high byte of SrcBuf address (0x07)
movwf TXADDRH ;Load upper four bits of the TXADDR register
movlw LOW(SrcBuf) ;Get low byte of the SrcBuf address (0x00)
movwf TXADDRL ;Load lower eight bits of the TXADDR register
movlw 0x01 ;Lets move 0x200 (512) bytes in one DMA xfer
movwf DMABCH ;Load the upper two bits of DMABC register
movlw 0xFF ;Actual bytes transferred is (DMABC + 1), so
movwf DMABCL ;we load 0x01FF into DMABC to xfer 0x200 bytes
BeginXfer:
bsf DMACON1, DMAEN ;The SPI DMA module will now begin transferring
;the data taken from SrcBuf, and will store
;received bytes into DestBuf.
;Execute whatever ;CPU is now free to do whatever it wants to
;and the DMA operation will continue without
;intervention, until it completes.
;When the transfer is complete, the SSP2IF flag in
;the PIR3 register will become set, and the DMAEN bit
;is automatically cleared by the hardware.
;The DestBuf (0x500-0x7FF) will contain the received
;data. To start another transfer, firmware will need
;to reinitialize RXADDR, TXADDR, DMABC and then
;set the DMAEN bit.
EXAMPLE 19-2: 512-BYTE SPI MASTER MODE Init AND TRANSFER (CONTINUED)