Microchip Technology MCU PIC PIC18F87K22-I/PTRSL TQFP-80 MCP PIC18F87K22-I/PTRSL Data Sheet
Product codes
PIC18F87K22-I/PTRSL
2009-2011 Microchip Technology Inc.
DS39960D-page 317
PIC18F87K22 FAMILY
21.4.10
I
2
C™ MASTER MODE
TRANSMISSION
Transmission of a data byte, a 7-bit address or the
other half of a 10-bit address, is accomplished by
simply writing a value to the SSPxBUF register. This
action will set the Buffer Full flag bit, BF, and allow the
Baud Rate Generator to begin counting and start the
next transmission. Each bit of address/data will be
shifted out onto the SDAx pin after the falling edge of
SCLx is asserted (see data hold time specification
Parameter 106). SCLx is held low for one Baud Rate
Generator rollover count (T
other half of a 10-bit address, is accomplished by
simply writing a value to the SSPxBUF register. This
action will set the Buffer Full flag bit, BF, and allow the
Baud Rate Generator to begin counting and start the
next transmission. Each bit of address/data will be
shifted out onto the SDAx pin after the falling edge of
SCLx is asserted (see data hold time specification
Parameter 106). SCLx is held low for one Baud Rate
Generator rollover count (T
BRG
). Data should be valid
before SCLx is released high (see data setup time
specification Parameter
specification Parameter
107). When the SCLx pin is
released high, it is held that way for T
BRG
. The data on
the SDAx pin must remain stable for that duration and
some hold time after the next falling edge of SCLx.
After the eighth bit is shifted out (the falling edge of the
eighth clock), the BF flag is cleared and the master
releases SDAx. This allows the slave device being
addressed to respond with an ACK bit during the ninth
bit time if an address match occurred, or if data was
received properly. The status of ACK is written into the
ACKDT bit on the falling edge of the ninth clock. If the
master receives an Acknowledge, the Acknowledge
Status bit, ACKSTAT, is cleared; if not, the bit is set.
After the ninth clock, the SSPxIF bit is set and the
master clock (Baud Rate Generator) is suspended until
the next data byte is loaded into the SSPxBUF, leaving
SCLx low and SDAx unchanged (
some hold time after the next falling edge of SCLx.
After the eighth bit is shifted out (the falling edge of the
eighth clock), the BF flag is cleared and the master
releases SDAx. This allows the slave device being
addressed to respond with an ACK bit during the ninth
bit time if an address match occurred, or if data was
received properly. The status of ACK is written into the
ACKDT bit on the falling edge of the ninth clock. If the
master receives an Acknowledge, the Acknowledge
Status bit, ACKSTAT, is cleared; if not, the bit is set.
After the ninth clock, the SSPxIF bit is set and the
master clock (Baud Rate Generator) is suspended until
the next data byte is loaded into the SSPxBUF, leaving
SCLx low and SDAx unchanged (
).
After the write to the SSPxBUF, each bit of the address
will be shifted out on the falling edge of SCLx until all
seven address bits and the R/W bit are completed. On
the falling edge of the eighth clock, the master will
deassert the SDAx pin, allowing the slave to respond
with an Acknowledge. On the falling edge of the ninth
clock, the master will sample the SDAx pin to see if the
address was recognized by a slave. The status of the
ACK bit is loaded into the ACKSTAT status bit
(SSPxCON2<6>). Following the falling edge of the
ninth clock transmission of the address, the SSPxIF
flag is set, the BF flag is cleared and the Baud Rate
Generator is turned off until another write to the
SSPxBUF takes place, holding SCLx low and allowing
SDAx to float.
will be shifted out on the falling edge of SCLx until all
seven address bits and the R/W bit are completed. On
the falling edge of the eighth clock, the master will
deassert the SDAx pin, allowing the slave to respond
with an Acknowledge. On the falling edge of the ninth
clock, the master will sample the SDAx pin to see if the
address was recognized by a slave. The status of the
ACK bit is loaded into the ACKSTAT status bit
(SSPxCON2<6>). Following the falling edge of the
ninth clock transmission of the address, the SSPxIF
flag is set, the BF flag is cleared and the Baud Rate
Generator is turned off until another write to the
SSPxBUF takes place, holding SCLx low and allowing
SDAx to float.
21.4.10.1
BF Status Flag
In Transmit mode, the BF bit (SSPxSTAT<0>) is set
when the CPU writes to SSPxBUF and is cleared when
all 8 bits are shifted out.
when the CPU writes to SSPxBUF and is cleared when
all 8 bits are shifted out.
21.4.10.2
WCOL Status Flag
If the user writes the SSPxBUF when a transmit is
already in progress (i.e., SSPxSR is still shifting out a
data byte), the WCOL bit is set and the contents of the
buffer are unchanged (the write doesn’t occur) after
already in progress (i.e., SSPxSR is still shifting out a
data byte), the WCOL bit is set and the contents of the
buffer are unchanged (the write doesn’t occur) after
2 T
CY
after the SSPxBUF write. If SSPxBUF is rewritten
within 2 T
CY
, the WCOL bit is set and SSPxBUF is
updated. This may result in a corrupted transfer.
The user should verify that the WCOL bit is clear after
each write to SSPxBUF to ensure the transfer is correct.
In all cases, WCOL must be cleared in software.
The user should verify that the WCOL bit is clear after
each write to SSPxBUF to ensure the transfer is correct.
In all cases, WCOL must be cleared in software.
21.4.10.3
ACKSTAT Status Flag
In Transmit mode, the ACKSTAT bit (SSPxCON2<6>)
is cleared when the slave has sent an Acknowledge
(ACK = 0) and is set when the slave does not Acknowl-
edge (ACK = 1). A slave sends an Acknowledge when
it has recognized its address (including a general call),
or when the slave has properly received its data.
is cleared when the slave has sent an Acknowledge
(ACK = 0) and is set when the slave does not Acknowl-
edge (ACK = 1). A slave sends an Acknowledge when
it has recognized its address (including a general call),
or when the slave has properly received its data.
21.4.11
I
2
C™ MASTER MODE RECEPTION
Master mode reception is enabled by programming the
Receive Enable bit, RCEN (SSPxCON2<3>).
Receive Enable bit, RCEN (SSPxCON2<3>).
The Baud Rate Generator begins counting, and on
each rollover, the state of the SCLx pin changes
(high-to-low/low-to-high) and data is shifted into the
SSPxSR. After the falling edge of the eighth clock, the
receive enable flag is automatically cleared, the con-
tents of the SSPxSR are loaded into the SSPxBUF, the
BF flag bit is set, the SSPxIF flag bit is set and the Baud
Rate Generator is suspended from counting, holding
SCLx low. The MSSP is now in Idle state awaiting the
next command. When the buffer is read by the CPU,
the BF flag bit is automatically cleared. The user can
then send an Acknowledge bit at the end of reception
by setting the Acknowledge Sequence Enable bit,
ACKEN (SSPxCON2<4>).
each rollover, the state of the SCLx pin changes
(high-to-low/low-to-high) and data is shifted into the
SSPxSR. After the falling edge of the eighth clock, the
receive enable flag is automatically cleared, the con-
tents of the SSPxSR are loaded into the SSPxBUF, the
BF flag bit is set, the SSPxIF flag bit is set and the Baud
Rate Generator is suspended from counting, holding
SCLx low. The MSSP is now in Idle state awaiting the
next command. When the buffer is read by the CPU,
the BF flag bit is automatically cleared. The user can
then send an Acknowledge bit at the end of reception
by setting the Acknowledge Sequence Enable bit,
ACKEN (SSPxCON2<4>).
21.4.11.1
BF Status Flag
In receive operation, the BF bit is set when an address
or data byte is loaded into SSPxBUF from SSPxSR. It
is cleared when the SSPxBUF register is read.
or data byte is loaded into SSPxBUF from SSPxSR. It
is cleared when the SSPxBUF register is read.
21.4.11.2
SSPOV Status Flag
In receive operation, the SSPOV bit is set when 8 bits
are received into the SSPxSR and the BF flag bit is
already set from a previous reception.
are received into the SSPxSR and the BF flag bit is
already set from a previous reception.
21.4.11.3
WCOL Status Flag
If the user writes the SSPxBUF when a receive is
already in progress (i.e., SSPxSR is still shifting in a
data byte), the WCOL bit is set and the contents of the
buffer are unchanged (the write doesn’t occur).
already in progress (i.e., SSPxSR is still shifting in a
data byte), the WCOL bit is set and the contents of the
buffer are unchanged (the write doesn’t occur).
Note:
The MSSP module must be in an inactive
state before the RCEN bit is set or the
RCEN bit will be disregarded.
state before the RCEN bit is set or the
RCEN bit will be disregarded.