PIC18F97J60_11 Datasheet, PDF (273/492 Pages) Microchip Technology – 64/80/100-Pin, High-Performance, 1-Mbit Flash Microcontrollers with Ethernet

PIC18F97J60 FAMILY
20.3.3 ENABLING SPI I/O
To enable the serial port, MSSP Enable bit, SSPEN
(SSPxCON1<5>), must be set. To reset or reconfigure
SPI mode, clear the SSPEN bit, reinitialize the
SSPxCON registers and then set the SSPEN bit. This
configures the SDIx, SDOx, SCKx and SSx pins as
serial port pins. For the pins to behave as the serial port
function, some must have their data direction bits (in
the TRIS register) appropriately programmed as
follows:
• SDIx is automatically controlled by the SPI module
• SDOx must have TRISC<5> (or TRISD<4>) bit
cleared
• SCKx (Master mode) must have TRISC<3> (or
TRISD<6>) bit cleared
• SCKx (Slave mode) must have TRISC<3> (or
TRISD<6>) bit set
• SSx must have TRISF<7> (or TRISD<7>) bit set
Any serial port function that is not desired may be
overridden by programming the corresponding data
direction (TRIS) register to the opposite value.
20.3.4 TYPICAL CONNECTION
Figure 20-2 shows a typical connection between two
microcontrollers. The master controller (Processor 1)
initiates the data transfer by sending the SCKx signal.
Data is shifted out of both shift registers on their
programmed clock edge and latched on the opposite
edge of the clock. Both processors should be
programmed to the same Clock Polarity (CKP), then
both controllers would send and receive data at the
same time. Whether the data is meaningful (or dummy
data) depends on the application software. This leads
to three scenarios for data transmission:
• Master sends data–Slave sends dummy data
• Master sends data–Slave sends data
• Master sends dummy data–Slave sends data
FIGURE 20-2:
SPI MASTER/SLAVE CONNECTION
SPI Master SSPM<3:0> = 00xxb
SDOx
Serial Input Buffer
(SSPxBUF)
SDIx
SPI Slave SSPM<3:0> = 010xb
Serial Input Buffer
(SSPxBUF)
Shift Register
(SSPxSR)
MSb
LSb
SDIx
PROCESSOR 1
SCKx
Serial Clock
SDOx
Shift Register
(SSPxSR)
MSb
LSb
SCKx
PROCESSOR 2
 2011 Microchip Technology Inc.
DS39762F-page 273