PIC12F1516 MICROCHIP [Microchip Technology], PIC12F1516 Datasheet - Page 190

• Manufacturer Part Number: PIC12F1516
• Description: 28/40/44-Pin Flash Microcontrollers with nanoWatt XLP Technology
• Manufacturer: MICROCHIP [Microchip Technology]

PIC16(L)F1516/7/8/9
21.2.2
When initializing the SPI, several options need to be
specified. This is done by programming the appropriate
control bits (SSPCON1<5:0> and SSPSTAT<7:6>).
These control bits allow the following to be specified:
• Master mode (SCK is the clock output)
• Slave mode (SCK is the clock input)
• Clock Polarity (Idle state of SCK)
• Data Input Sample Phase (middle or end of data
• Clock Edge (output data on rising/falling edge of
• Clock Rate (Master mode only)
• Slave Select mode (Slave mode only)
To enable the serial port, SSP Enable bit, SSPEN of the
SSPCON1 register, must be set. To reset or reconfig-
ure SPI mode, clear the SSPEN bit, re-initialize the
SSPCON registers and then set the SSPEN bit. This
configures the SDI, SDO, SCK and SS pins as serial
port pins. For the pins to behave as the serial port func-
tion, some must have their data direction bits (in the
TRIS register) appropriately programmed as follows:
• SDI must have corresponding TRIS bit set
• SDO must have corresponding TRIS bit cleared
• SCK (Master mode) must have corresponding
• SCK (Slave mode) must have corresponding
• SS must have corresponding TRIS bit set
Any serial port function that is not desired may be
overridden by programming the corresponding data
direction (TRIS) register to the opposite value.
FIGURE 21-5:
DS41452B-page 190
output time)
SCK)
TRIS bit cleared
TRIS bit set
SPI MODE OPERATION
SPI Master SSPM<3:0> = 00xx
MSb
Serial Input Buffer
Processor 1
Shift Register
SPI MASTER/SLAVE CONNECTION
(SSPSR)
(BUF)
= 1010
LSb
General I/O
SCK
SDO
SDI
Preliminary
Serial Clock
Slave Select
(optional)
The MSSP consists of a transmit/receive shift register
(SSPSR) and a buffer register (SSPBUF). The SSPSR
shifts the data in and out of the device, MSb first. The
SSPBUF holds the data that was written to the SSPSR
until the received data is ready. Once the 8 bits of data
have been received, that byte is moved to the SSPBUF
register. Then, the Buffer Full Detect bit, BF of the
SSPSTAT register, and the interrupt flag bit, SSPIF, are
set. This double-buffering of the received data
(SSPBUF) allows the next byte to start reception before
reading the data that was just received. Any write to the
SSPBUF register during transmission/reception of data
will be ignored and the write collision detect bit WCOL
of the SSPCON1 register, will be set. User software
must clear the WCOL bit to allow the following write(s)
to the SSPBUF register to complete successfully.
When the application software is expecting to receive
valid data, the SSPBUF should be read before the next
byte of data to transfer is written to the SSPBUF. The
Buffer Full bit, BF of the SSPSTAT register, indicates
when SSPBUF has been loaded with the received data
(transmission is complete). When the SSPBUF is read,
the BF bit is cleared. This data may be irrelevant if the
SPI is only a transmitter. Generally, the MSSP interrupt
is used to determine when the transmission/reception
has completed. If the interrupt method is not going to
be used, then software polling can be done to ensure
that a write collision does not occur.
The SSPSR is not directly readable or writable and can
only be accessed by addressing the SSPBUF register.
Additionally, the SSPSTAT register indicates the
various Status conditions.
SCK
SDO
SDI
SS
SPI Slave SSPM<3:0> = 010x
MSb
Serial Input Buffer
Shift Register
(SSPBUF)
(SSPSR)
Processor 2
 2011 Microchip Technology Inc.
LSb