PIC18LF24K Datasheet, PDF (370/594 Pages) –

PIC18(L)F26/45/46K40
26.9.8
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 device. 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 a reserved address in the
I²C protocol, defined as address 0x00. When the
GCEN bit of the SSPxCON2 register is set, the slave
module will automatically ACK the reception of this
address regardless of the value stored in SSPxADD.
After the slave clocks in an address of all zeros with
the R/W bit clear, an interrupt is generated and slave
software can read SSPxBUF and respond.
Figure 26-24 shows a general call reception
sequence.
In 10-bit Address mode, the UA bit will not be set on
the reception of the general call address. The slave
will prepare to receive the second byte as data, just as
it would in 7-bit mode.
If the AHEN bit of the SSPxCON3 register is set, just
as with any other address reception, the slave
hardware will stretch the clock after the eighth falling
edge of SCL. The slave must then set its ACKDT
value and release the clock with communication
progressing as it would normally.
26.9.9 SSP MASK REGISTER
An SSP Mask (SSPxMSK) register (Register 26-12) is
available in I²C Slave mode as a mask for the value
held in the SSPSR register during an address
comparison operation. A zero (‘0’) bit in the SSPxMSK
register has the effect of making the corresponding bit
of the received address a “don’t care”.
This register is reset to all ‘1’s upon any Reset
condition and, therefore, has no effect on standard
SSP operation until written with a mask value.
The SSP Mask register is active during:
• 7-bit Address mode: address compare of A<7:1>.
10-bit Address mode: address compare of A<7:0>
only. The SSP mask has no effect during the reception
of the first (high) byte of the address.
FIGURE 26-24: SLAVE MODE GENERAL CALL ADDRESS SEQUENCE
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
SSPxIF
S
1 2 34 5 6 78 91 2 34 5 6 78 9
BF (SSPxSTAT<0>)
GCEN (SSPxCON2<7>)
Cleared by software
SSPxBUF is read
’1’
 2016 Microchip Technology Inc.
Preliminary
DS40001816C-page 370