PIC18LF4610T-I Datasheet, PDF (174/376 Pages) Microchip Technology – 28/40/44-Pin Flash Microcontrollers

PIC18F2X1X/4X1X
16.4.5 GENERAL CALL ADDRESS
SUPPORT
The addressing procedure for the I²C bus is such that
the first byte after the Start condition usually deter-
mines 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, 8 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 Address 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 Address 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 16-15).
FIGURE 16-15:
SLAVE MODE GENERAL CALL ADDRESS SEQUENCE
(7 OR 10-BIT ADDRESS 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’
DS39636D-page 176
© 2009 Microchip Technology Inc.