PIC18F26K80-I Datasheet, PDF (315/622 Pages) Microchip Technology – 28/40/44/64-Pin, Enhanced Flash Microcontrollers with ECAN™ and nanoWatt XLP Technology

PIC18F66K80 FAMILY
21.4.5
GENERAL CALL ADDRESS
SUPPORT
The addressing procedure for the I²C bus is such that
the first byte after the Start condition usually
determines which device will be the slave addressed by
the master. The exception is the general call address
which can address all devices. When this address is
used, all devices should, in theory, respond with an
Acknowledge.
The general call address is one of eight addresses
reserved for specific purposes by the I²C protocol. It
consists of all ‘0’s with R/W = 0.
The general call address is recognized when the
General Call Enable bit, GCEN, is enabled
(SSPCON2<7> set). Following a Start bit detect, eight
bits are shifted into the SSPSR and the address is
compared against the SSPADD. It is also compared to
the general call address and fixed in hardware.
If the general call address matches, the SSPSR is
transferred to the SSPBUF, the BF flag bit is set (eighth
bit), and on the falling edge of the ninth bit (ACK bit),
the SSPIF interrupt flag bit is set.
When the interrupt is serviced, the source for the
interrupt can be checked by reading the contents of the
SSPBUF. The value can be used to determine if the
address was device-specific or a general call address.
In 10-Bit Addressing mode, the SSPADD is required to
be updated for the second half of the address to match
and the UA bit is set (SSPSTAT<1>). If the general call
address is sampled when the GCEN bit is set, while the
slave is configured in 10-Bit Addressing mode, then the
second half of the address is not necessary, the UA bit
will not be set and the slave will begin receiving data
after the Acknowledge (Figure 21-17).
FIGURE 21-17:
SLAVE MODE GENERAL CALL ADDRESS SEQUENCE
(7 OR 10-BIT ADDRESSING MODE)
SDA
General Call Address
Address is Compared to General Call Address
after ACK, set interrupt
R/W = 0
Receiving Data
ACK
ACK D7 D6 D5 D4 D3 D2 D1 D0
SCL
SSPIF
S
1 2 34 5 6 78 91 2 34 5 6 78 9
BF (SSPSTAT<0>)
SSPOV (SSPCON1<6>)
GCEN (SSPCON2<7>)
Cleared in software
SSPBUF is read
‘0’
‘1’
 2010-2012 Microchip Technology Inc.
DS39977F-page 315