PIC16F74-ESLASHML datasheet(64/174 Pages) MICROCHIP

64 / 174 page

PIC16F7X

DS30325B-page 62

 2002 Microchip Technology Inc.

FIGURE 9-1:

SSP BLOCK DIAGRAM

(SPI MODE)

To enable the serial port, SSP enable bit, SSPEN

(SSPCON<5>) must be set. To reset or reconfigure SPI

mode, clear bit SSPEN, re-initialize the SSPCON reg-

ister, and then set bit SSPEN. This configures the SDI,

SDO, SCK, and SS pins as serial port pins. For the pins

to behave as the serial port function, they must have

their data direction bits (in the TRISC register) appro-

priately programmed. That is:

• SDI must have TRISC<4> set

• SDO must have TRISC<5> cleared

• SCK (Master mode) must have TRISC<3>

cleared

• SCK (Slave mode) must have TRISC<3> set

• SS must have TRISA<5> set and ADCON must

be configured such that RA5 is a digital I/O

Read

Write

Internal

Data Bus

RC4/SDI/SDA

RC5/SDO

RA5/SS/AN4

RC3/SCK/

SSPSR reg

SSPBUF reg

SSPM3:SSPM0

bit0

Shift

Clock

SS Control

Enable

Edge

Select

Clock Select

TMR2 Output

TCY

Prescaler

4, 16, 64

TRISC<3>

Edge

Select

SCL

Peripheral OE

Note 1: When the SPI is in Slave mode with SS pin

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

the SPI module will reset if the SS pin is set

to VDD.

2: If the SPI is used in Slave mode with

CKE = '1', then the SS pin control must be

enabled.

3: 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 module into PORTC controls the

state

that

read

back

from

the

TRISC<5> bit (see Section 4.3 for infor-

mation on PORTC). If 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.

PIC16F74-E/ML Datasheet(PDF) 64 Page - Microchip Technology

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