PIC16F87-E Datasheet, PDF (97/228 Pages) Microchip Technology – 18/20/28-Pin Enhan lashMicrocontrollers with nanoWatt Technology

PIC16F87/88
10.3.2 MASTER MODE OPERATION
Master mode 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 dis-
abled. 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 operation, the SCL and SDA lines are
manipulated in firmware by clearing the corresponding
TRISB<4,1> bit(s). The output level is always low, irre-
spective of the value(s) in PORTB<4,1>. So, when
transmitting data, a ‘1’ data bit must have the
TRISB<1> bit set (input) and a ‘0’ data bit must have
the TRISB<1> bit cleared (output). The same scenario
is true for the SCL line with the TRISB<4> 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 the SSP Interrupt Flag
bit, SSPIF, to be set (SSP Interrupt if enabled):
• Start condition
• Stop condition
• Data transfer byte transmitted/received
Master mode operation can be done with either the
Slave mode Idle (SSPM3:SSPM0 = 1011), or with the
Slave mode active. When both Master mode operation
and Slave modes are used, the software needs to
differentiate the source(s) of the interrupt.
For more information on Master mode operation, see
Application Note AN554, “Software Implementation of
I²C™ Bus Master”.
10.3.3 MULTI-MASTER MODE OPERATION
In Multi-Master mode operation, the interrupt genera-
tion 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 operation, the SDA line must be
monitored to see if the signal level is the expected out-
put 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 TRISB<4,1>). There are two stages
where this arbitration can be lost:
• Address Transfer
• Data Transfer
When the slave logic is enabled, the slave device
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
generated. If arbitration was lost during the data
transfer stage, the device will need to retransfer the
data at a later time.
For more information on Multi-Master mode operation,
see Application Note AN578, “Use of the SSP Module
in the of I²C™ Multi-Master Environment”.
TABLE 10-3: REGISTERS ASSOCIATED WITH I²C™ OPERATION
Address 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
0Bh, 8Bh, INTCON
10Bh,18Bh
0Ch
PIR1
8Ch
PIE1
GIE PEIE TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF
— ADIF⁽¹⁾ RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF
— ADIE⁽¹⁾ RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE
13h
SSPBUF Synchronous Serial Port Receive Buffer/Transmit Register
93h
SSPADD Synchronous Serial Port (I²C mode) Address Register
14h
SSPCON WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0
94h
SSPSTAT SMP⁽²⁾ CKE⁽²⁾ D/A
P
S
R/W UA
BF
86h
TRISB PORTB Data Direction Register
Legend:
Note 1:
2:
x = unknown, u = unchanged, - = unimplemented locations read as ‘0’.
Shaded cells are not used by SSP module in SPI™ mode.
This bit is only implemented on the PIC16F88. The bit will read ‘0’ on the PIC16F87.
Maintain these bits clear in I²C™ mode.
0000 000x
-000 0000
-000 0000
xxxx xxxx
0000 0000
0000 0000
0000 0000
1111 1111
0000 000u
-000 0000
-000 0000
uuuu uuuu
0000 0000
0000 0000
0000 0000
1111 1111
 2005 Microchip Technology Inc.
DS30487C-page 95