PIC18F6390 Datasheet, PDF (163/412 Pages) Microchip Technology – 64/80-Pin Flash Microcontrollers with LCD Driver and nanoWatt Technology

PIC18F6390/6490/8390/8490
15.3.3 ENABLING SPI I/O
To enable the serial port, SSP Enable bit, SSPEN
(SSPCON1<5>), must be set. To reset or reconfigure
SPI mode, clear the SSPEN bit, reinitialize the
SSPCON registers and then set the SSPEN bit. This
configures the SDI, SDO, SCK and SS pins as serial
port pins. For the pins to behave as the serial port func-
tion, some must have their data direction bits (in the
TRIS register) appropriately programmed as follows:
• SDI is automatically controlled by the SPI module
• SDO must have TRISC<5> bit cleared
• SCK (Master mode) must have TRISC<3> bit
cleared
• SCK (Slave mode) must have TRISC<3> bit set
• SS must have TRISF<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.
15.3.4 TYPICAL CONNECTION
Figure 15-2 shows a typical connection between two
microcontrollers. The master controller (Processor 1)
initiates the data transfer by sending the SCK 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 15-2:
SPI™ MASTER/SLAVE CONNECTION
SPI™ Master SSPM3:SSPM0 = 00xx
SDO
Serial Input Buffer
(SSPBUF)
SPI™ Slave SSPM3:SSPM0 = 010x
SDI
Serial Input Buffer
(SSPBUF)
Shift Register
(SSPSR)
MSb
LSb
PROCESSOR 1
SDI
Serial Clock
SCK
SDO
Shift Register
(SSPSR)
MSb
LSb
SCK
PROCESSOR 2
 2004 Microchip Technology Inc.
Preliminary
DS39629B-page 161