PIC16F747 Microchip Technology Inc., PIC16F747 Datasheet - Page 99

• Manufacturer Part Number: PIC16F747
• Description: 28/40/44-pin, 8-bit Cmos Flash Microcontrollers With 10-bit A/d And Nanowatt Technology
• Manufacturer: Microchip Technology Inc.

10.3.3
To enable the serial port, SSP Enable bit, SSPEN
(SSPCON<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
function, some must have their data direction bits (in
the TRIS register) appropriately programmed. That is:
• SDI is automatically controlled by the SPI module
• SDO must have TRISC<5> bit cleared
• SCK (Master mode) must have TRISC<3> bit
• SCK (Slave mode) must have TRISC<3> bit set
• SS must have TRISA<5> 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.
FIGURE 10-2:
 2004 Microchip Technology Inc.
cleared
SPI™ Master SSPM3:SSPM0 = 00xxb
ENABLING SPI I/O
MSb
PROCESSOR 1
Serial Input Buffer
SPI™ MASTER/SLAVE CONNECTION
Shift Register
(SSPBUF)
(SSPSR)
LSb
SDO
SCK
SDI
Serial Clock
10.3.4
Figure 10-2 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 pro-
grammed 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
SDO
SCK
SDI
SPI™ Slave SSPM3:SSPM0 = 010xb
TYPICAL CONNECTION
MSb
Serial Input Buffer
Shift Register
PROCESSOR 2
(SSPBUF)
(SSPSR)
PIC16F7X7
LSb
DS30498C-page 97