PIC18F25J50 MICROCHIP [Microchip Technology], PIC18F25J50 Datasheet - Page 307

• Manufacturer Part Number: PIC18F25J50
• Description: 28/44-Pin, Low-Power, High-Performance USB Microcontrollers with nanoWatt XLP Technology
• Manufacturer: MICROCHIP [Microchip Technology]

19.5.5
The addressing procedure for the I
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
General
(SSPxCON2<7> is set). Following a Start bit detect,
8 bits are shifted into the SSPxSR and the address is
compared against the SSPxADD. It is also compared to
the general call address and fixed in hardware.
FIGURE 19-17:
 2011 Microchip Technology Inc.
GCEN (SSPxCON2<7>)
SSPOV (SSPxCON1<6>)
SDAx
SCLx
SSPxIF
BF (SSPxSTAT<0>)
Call
GENERAL CALL ADDRESS
SUPPORT
Enable
S
SLAVE MODE GENERAL CALL ADDRESS SEQUENCE
(7-BIT OR 10-BIT ADDRESSING MODE)
bit,
1
2
GCEN,
General Call Address
2
C bus is such that
3
2
4
C protocol. It
is
5
enabled
6
7
R/W = 0
8
PIC18F46J50 FAMILY
If the general call address matches, the SSPxSR is
transferred to the SSPxBUF, the BF flag bit is set (eighth
bit), and on the falling edge of the ninth bit (ACK bit), the
SSPxIF interrupt flag bit is set.
When the interrupt is serviced, the source for the
interrupt can be checked by reading the contents of the
SSPxBUF. The value can be used to determine if the
address was device-specific or a general call address.
In 10-bit mode, the SSPxADD is required to be updated
for the second half of the address to match and the UA
bit is set (SSPxSTAT<1>). If the general call address is
sampled when the GCEN bit is set, while the slave is
configured in 10-Bit Addressing 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
ACK
Address is compared to General Call Address
after ACK, set interrupt
9
D7
1
D6
2
Cleared in software
SSPxBUF is read
(Figure
Receiving Data
D5
3
D4
4
19-17).
D3
5
D2
6
D1
7
DS39931D-page 307
D0
8
ACK
9
‘0’
‘1’