PIC16F877-20L Datasheet, PDF (78/218 Pages) Microchip Technology – 28/40-Pin 8-Bit CMOS FLASH Microcontrollers

PIC16F87X
9.2.5 MASTER MODE
Master mode of operation is supported by interrupt
generation on the detection of the START and STOP
conditions. The STOP (P) and START (S) bits are
cleared from a RESET, or when the MSSP module is
disabled. Control of the I²C bus may be taken when the
P bit is set, or the bus is idle, with both the S and P bits
clear.
In Master mode, the SCL and SDA lines are manipu-
lated by the MSSP hardware.
The following events will cause the SSP Interrupt Flag
bit, SSPIF, to be set (an SSP interrupt will occur if
enabled):
• START condition
• STOP condition
• Data transfer byte transmitted/received
• Acknowledge transmit
• Repeated START
FIGURE 9-9:
SSP BLOCK DIAGRAM (I²C MASTER MODE)
Read
Internal
Data Bus
Write
SSPM3:SSPM0,
SSPADD<6:0>
SDA
SDA in
SSPBUF
SSPSR
MSb
Shift
Clock
LSb
Baud
Rate
Generator
START bit, STOP bit,
Acknowledge
Generate
SCL
SCL in
Bus Collision
START bit Detect,
STOP bit Detect
Write Collision Detect
Clock Arbitration
State Counter for
end of XMIT/RCV
Set/Reset, S, P, WCOL (SSPSTAT)
Set SSPIF, BCLIF
Reset ACKSTAT, PEN (SSPCON2)
9.2.6 MULTI-MASTER MODE
In Multi-Master mode, the interrupt generation on the
detection of the START and STOP conditions allows
the determination of when the bus is free. The STOP
(P) and START (S) bits are cleared from a RESET or
when the MSSP module is disabled. Control of the I²C
bus may be taken when bit P (SSPSTAT<4>) is set, or
the bus is idle with both the S and P bits clear. When
the bus is busy, enabling the SSP Interrupt will gener-
ate the interrupt when the STOP condition occurs.
In Multi-Master operation, the SDA line must be moni-
tored for arbitration to see if the signal level is the
expected output level. This check is performed in hard-
ware, with the result placed in the BCLIF bit.
The states where arbitration can be lost are:
• Address Transfer
• Data Transfer
• A START Condition
• A Repeated START Condition
• An Acknowledge Condition
DS30292D-page 78
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