PIC18F2331_07 Datasheet, PDF (224/400 Pages) Microchip Technology – 28/40/44-Pin Enhanced Flash Microcontrollers with nanoWatt Technology, High Performance PWM and A/D

PIC18F2331/2431/4331/4431
18.3.2 MASTER MODE
Master mode of operation is supported in firmware
using interrupt generation on the detection of the Start
and Stop conditions. The Stop (P) and Start (S) bits are
cleared from a Reset or when the SSP module is
disabled. The Stop (P) and Start (S) bits will toggle
based on the Start and Stop conditions. Control of the
I²C bus may be taken when the P bit is set, or the bus
is Idle and both the S and P bits are clear.
In Master mode, the SCL and SDA lines are manipu-
lated by clearing the corresponding TRISC<5:4> or
TRISD<3:2> bits. The output level is always low,
regardless of the value(s) in PORTC<5:4> or
PORTD<3:2>. So when transmitting data, a ‘1’ data bit
must have the TRISC<4> bit set (input) and a ‘0’ data
bit must have the TRISC<4> bit cleared (output). The
same scenario is true for the SCL line with the
TRISC<4> or TRISD<2> bit. Pull-up resistors must be
provided externally to the SCL and SDA pins for proper
operation of the I²C module.
The following events will cause SSP Interrupt Flag bit,
SSPIF, to be set (SSP interrupt will occur if enabled):
• Start condition
• Stop condition
• Data transfer byte transmitted/received
Master mode of operation can be done with either the
Slave mode Idle (SSPM3:SSPM0 = 1011) or with the
Slave active. When both Master and Slave modes are
enabled, the software needs to differentiate the
source(s) of the interrupt.
18.3.3 MULTI-MASTER MODE
In Multi-Master mode, the interrupt generation on the
detection of the Start and Stop conditions allows the
determination of when the bus is free. The Stop (P) and
Start (S) bits are cleared from a Reset or when the SSP
module is disabled. The Stop (P) and Start (S) bits will
toggle based on the Start and Stop conditions. Control
of the I²C bus may be taken when bit P (SSPSTAT<4>)
is set, or the bus is Idle and both the S and P bits clear.
When the bus is busy, enabling the SSP interrupt will
generate the interrupt when the Stop condition occurs.
In Multi-Master mode, the SDA line must be monitored
to see if the signal level is the expected output level.
This check only needs to be done when a high level is
output. If a high level is expected and a low level is
present, the device needs to release the SDA and SCL
lines (set TRISC<5:4> or TRISD<3:2>). There are two
stages where this arbitration can be lost, these are:
• Address Transfer
• Data Transfer
When the slave logic is enabled, the slave continues to
receive. If arbitration was lost during the address
transfer stage, communication to the device may be in
progress. If addressed, an ACK pulse will be gener-
ated. If arbitration was lost during the data transfer
stage, the device will need to retransfer the data at a
later time.
TABLE 18-3: REGISTERS ASSOCIATED WITH I²C™ OPERATION
Name
Bit 7
Bit 6
Bit 5 Bit 4 Bit 3
Bit 2
Bit 1
Bit 0
Value on:
POR, BOR
Value on
all other
Resets
INTCON GIE/GIEH PEIE/GIEL TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 0000 000x 0000 000u
PIR1
—
ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF -000 0000 -000 0000
PIE1
—
ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE -000 0000 -000 0000
SSPBUF SSP Receive Buffer/Transmit Register
SSPADD SSP Address Register (I²C mode)
xxxx xxxx uuuu uuuu
0000 0000 0000 0000
SSPCON WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 0000 0000 0000 0000
SSPSTAT SMP⁽¹⁾ CKE⁽¹⁾ D/A
P
TRISC⁽²⁾ PORTC Data Direction Register
TRISD⁽²⁾ PORTD Data Direction Register
S
R/W UA
BF 0000 0000 0000 0000
1111 1111 1111 1111
1111 1111 1111 1111
Legend: x = unknown, u = unchanged, - = unimplemented, read as ‘0’. Shaded cells are not used by the SSP
module in I²C mode.
Note 1: Maintain these bits clear in I²C mode.
2: Depending upon the setting of SSPMX in CONFIG3H, these pins are multiplexed to PORTC or PORTD.
DS39616C-page 222
Preliminary
© 2007 Microchip Technology Inc.