PIC16F882_09 Datasheet, PDF (194/328 Pages) Microchip Technology – 28/40/44-Pin, Enhanced Flash-Based 8-Bit CMOS Microcontrollers with nanoWatt Technology

PIC16F882/883/884/886/887
13.4.2 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 (enabled) when
the General Call Enable (GCEN) bit is set (SSPCON2
register). 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 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 inter-
rupt 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 mode, the SSPADD is required to be updated
for the second half of the address to match, and the UA
bit is set (SSPSTAT register). If the general call address
is sampled when the GCEN bit is set, and 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 13-9).
FIGURE 13-9:
SLAVE MODE GENERAL CALL ADDRESS SEQUENCE (7 OR 10-BIT ADDRESS)
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
SSPOV
Cleared in software
SSPBUF is read
‘0’
GCEN
‘1’
DS41291F-page 192
© 2009 Microchip Technology Inc.