PIC18F87J11_12 Datasheet, PDF (268/466 Pages) Microchip Technology – 64/80-Pin, High-Performance, 1-Mbit Flash Microcontrollers

PIC18F87J11 FAMILY
20.4.6 MASTER MODE
Master mode is enabled by setting and clearing the
appropriate SSPMx bits in SSPxCON1 and by setting
the SSPEN bit. In Master mode, the SCLx and SDAx
lines are manipulated by the MSSP hardware if the
TRIS bits are set.
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 Firmware Controlled Master mode, user code
conducts all I²C bus operations based on Start and
Stop bit conditions.
Once Master mode is enabled, the user has six
options.
1. Assert a Start condition on SDAx and SCLx.
2. Assert a Repeated Start condition on SDAx and
SCLx.
3. Write to the SSPxBUF register, initiating
transmission of data/address.
4. Configure the I²C port to receive data.
5. Generate an Acknowledge condition at the end
of a received byte of data.
6. Generate a Stop condition on SDAx and SCLx.
Note:
The MSSPx module, when configured in
I²C Master mode, does not allow queueing
of events. For instance, the user is not
allowed to initiate a Start condition and
immediately write the SSPxBUF register
to initiate transmission before the Start
condition is complete. In this case, the
SSPxBUF will not be written to and the
WCOL bit will be set, indicating that a write
to the SSPxBUF did not occur.
The following events will cause the MSSPx Interrupt
Flag bit, SSPxIF, to be set (and MSSP interrupt, if
enabled):
• Start condition
• Stop condition
• Data transfer byte transmitted/received
• Acknowledge transmitted
• Repeated Start
FIGURE 20-18: MSSPx BLOCK DIAGRAM (I²C™ MASTER MODE)
SDAx
Read
Internal
Data Bus
Write
SSPxBUF
SDAx In
SSPxSR
MSb
Shift
Clock
LSb
SSPM<3:0>
SSPxADD<6:0>
Baud
Rate
Generator
SCLx
Start bit, Stop bit,
Acknowledge
Generate
SCLx 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 (SSPxSTAT), WCOL (SSPxCON1);
Set SSPxIF, BCLxIF;
Reset ACKSTAT, PEN (SSPxCON2)
DS39778E-page 268
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