PIC16F87XA datasheet(73/234 Pages) MICROCHIP

73 / 234 page

 2003 Microchip Technology Inc.

DS39582B-page 71

PIC16F87XA

9.0

MASTER SYNCHRONOUS

SERIAL PORT (MSSP)

MODULE

9.1

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,

display 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:

•Master mode

• Multi-Master mode

• Slave mode

9.2

Control Registers

The MSSP module has three associated registers.

These include a status register (SSPSTAT) and two

control registers (SSPCON 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.

Additional details are provided under the individual

sections.

9.3

SPI Mode

The SPI mode allows 8 bits of data to be synchronously

transmitted and received simultaneously. All four

modes

SPI

are

supported.

accomplish

communication, typically three pins are used:

• Serial Data Out (SDO) – RC5/SDO

• Serial Data In (SDI) – RC4/SDI/SDA

• Serial Clock (SCK) – RC3/SCK/SCL

Additionally, a fourth pin may be used when in a Slave

mode of operation:

• Slave Select (SS) – RA5/AN4/SS/C2OUT

Figure 9-1 shows the block diagram of the MSSP

module when operating in SPI mode.

FIGURE 9-1:

MSSP BLOCK DIAGRAM

(SPI MODE)

Note:

When the SPI is in Slave mode with SS pin

control enabled (SSPCON<3:0> = 0100),

the state of the SS pin can affect the state

read back from the TRISC<5> bit. The

Peripheral OE signal from the SSP mod-

ule in PORTC controls the state that is

read back from the TRISC<5> bit (see

Section 4.3 “PORTC and the TRISC

Read-Modify-Write instructions, such as

BSF

, are performed on the TRISC register

while the SS pin is high, this will cause the

TRISC<5> bit to be set, thus disabling the

SDO output.

Read

Write

Internal

Data Bus

SSPSR reg

SSPM3:SSPM0

bit0

Shift

Clock

SS Control

Enable

Edge

Select

Clock Select

TMR2 Output

TOSC

Prescaler

4, 16, 64

Edge

Select

Data to TX/RX in SSPSR

TRIS bit

SMP:CKE

RC5/SDO

(

)

SSPBUF reg

RC4/SDI/SDA

RA5/AN4/

RC3/SCK/SCL

Peripheral OE

SS/C2OUT

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