PIC18FXX20
17.3 SPI Mode
17.0 MASTER SYNCHRONOUS
SERIAL PORT (MSSP)
MODULE
The SPI mode allows 8 bits of data to be synchronously
transmitted and received simultaneously. All four
modes of SPI are supported. To accomplish communi-
cation, typically three pins are used:
• Serial Data Out (SDO) - RC5/SDO
• Serial Data In (SDI) - RC4/SDI/SDA
• Serial Clock (SCK) - RC3/SCK/SCL/LVDIN
Additionally, a fourth pin may be used when in a Slave
mode of operation:
• Slave Select (SS) - RF7/SS
17.1 Master SSP (MSSP) Module
Overview
The Master Synchronous Serial Port (MSSP) module is
a serial interface, useful for communicating with other
peripheral or microcontroller devices. These peripheral
devices may be serial EEPROMs, shift registers, dis-
play drivers, A/D converters, etc. The MSSP module
can operate in one of two modes:
• Serial Peripheral Interface (SPI)
• Inter-Integrated Circuit (I2C)
- Full Master mode
- Slave mode (with general address call)
The I2C interface supports the following modes in
hardware:
Figure 17-1 shows the block diagram of the MSSP
module when operating in SPI mode.
FIGURE 17-1:
MSSP BLOCK DIAGRAM
(SPI MODE)
Internal
Data Bus
• Master mode
• Multi-Master mode
• Slave mode
Read
Write
SSPBUF reg
SSPSR reg
17.2 Control Registers
RC4/SDI/SDA
RC5/SDO
The MSSP module has three associated registers.
These include a status register (SSPSTAT) and two
control registers (SSPCON1 and SSPCON2). The use
of these registers and their individual configuration bits
differ significantly, depending on whether the MSSP
module is operated in SPI or I2C mode.
Shift
bit0
Clock
Additional details are provided under the individual
sections.
RF7/SS
Control
Enable
SS
Edge
Select
2
Clock Select
SSPM3:SSPM0
SMP:CKE
4
TMR2 Output
RC3/SCK/
SCL
(
)
2
2
Edge
Select
TOSC
Prescaler
4, 16, 64
Data to TX/RX in SSPSR
TRIS bit
2003 Microchip Technology Inc.
Advance Information
DS39609A-page 157
MICROCHIP [ MICROCHIP ]
