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PIC16F87XATI/SP Datasheet - Page 94

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PIC16F87XA
9.4.5
GENERAL CALL ADDRESS
SUPPORT
2
The addressing procedure for the I
C 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 I
consists of all ‘0’s with R/W = 0.
The general call address is recognized when the Gen-
eral 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.
FIGURE 9-15:
SLAVE MODE GENERAL CALL ADDRESS SEQUENCE
(7 OR 10-BIT ADDRESS MODE)
General Call Address
SDA
SCL
1
2
3
S
SSPIF
BF (SSPSTAT<0>)
SSPOV (SSPCON<6>)
GCEN (SSPCON2<7>)
DS39582C-page 94
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 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
2
for the second half of the address to match and the UA
C protocol. It
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 9-15).
Address is compared to general call address.
After ACK, set interrupt.
R/W = 0
ACK
D7
D6
4
5
6
7
8
9
1
2
Cleared in software
SSPBUF is read
Receiving Data
ACK
D5
D4
D3
D2
D1
D0
3
4
5
6
7
8
9
‘0’
‘1’
 2001-2013 Microchip Technology Inc.

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