PIC18C242 MICROCHIP [Microchip Technology], PIC18C242 Datasheet - Page 133

• Manufacturer Part Number: PIC18C242
• Description: High-Performance Microcontrollers with 10-Bit A/D
• Manufacturer: MICROCHIP [Microchip Technology]

14.3.2
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 acknowl-
edge.
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 14-12: SLAVE MODE GENERAL CALL ADDRESS SEQUENCE (7 OR 10-BIT ADDRESS
7/99 Microchip Technology Inc.
GCEN (SSPCON2<7>)
SSPOV (SSPCON1<6>)
SDA
SCL
SSPIF
BF (SSPSTAT<0>)
GENERAL CALL ADDRESS SUPPORT
MODE)
S
1
2
General Call Address
2
C bus is such that
3
2
4
C protocol. It
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 (eight
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 14-12).
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
D3
PIC18CXX2
5
D2
6
D1
7
DS39026B-page 133
D0
8
ACK
9
’0’
’1’