PIC18F258 MICROCHIP [Microchip Technology], PIC18F258 Datasheet - Page 166

• Manufacturer Part Number: PIC18F258
• Description: High Performance, 28/40-Pin Enhanced FLASH Microcontrollers with CAN
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18FXX8
17.4.5
The addressing procedure for the I
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 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 17-15:
DS41159B-page 164
GCEN (SSPCON2<7>)
SSPOV (SSPCON1<6>)
SDA
SCL
SSPIF
BF (SSPSTAT<0>)
GENERAL CALL ADDRESS
SUPPORT
S
SLAVE MODE GENERAL CALL ADDRESS SEQUENCE
(7 OR 10-BIT ADDRESS MODE)
1
2
General Call Address
2
C bus is such that
3
2
C protocol. It
4
5
6
Preliminary
7
R/W = 0
8
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
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 17-15).
ACK
Address is compared to General Call Address
after ACK, set interrupt
9
D7
1
D6
2
Cleared in software
SSPBUF is read
Receiving data
D5
3
D4
4
 2002 Microchip Technology Inc.
D3
5
D2
6
D1
7
D0
8
ACK
9
’0’
’1’