PIC16F1513T-I/SS View Datasheet(PDF) - Microchip Technology
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PIC16F1513T-I/SS Datasheet PDF : 360 Pages
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PIC16(L)F1512/3
FIGURE 20-4:
SPI MASTER AND MULTIPLE SLAVE CONNECTION
SPI Master
SCK
SDO
SDI
General I/O
General I/O
General I/O
SCK
SDI
SDO
SS
SPI Slave
#1
SCK
SDI
SDO
SS
SPI Slave
#2
SCK
SDI
SDO
SS
SPI Slave
#3
20.2.1 SPI MODE REGISTERS
The MSSP module has five registers for SPI mode
operation. These are:
• MSSP STATUS register (SSPSTAT)
• MSSP Control Register 1 (SSPCON1)
• MSSP Control Register 3 (SSPCON3)
• MSSP Data Buffer register (SSPBUF)
• MSSP Address register (SSPADD)
• MSSP Shift Register (SSPSR)
(Not directly accessible)
SSPCON1 and SSPSTAT are the control and STATUS
registers in SPI mode operation. The SSPCON1
register is readable and writable. The lower six bits of
the SSPSTAT are read-only. The upper two bits of the
SSPSTAT are read/write.
In SPI master mode, SSPADD can be loaded with a
value used in the Baud Rate Generator. More
information on the Baud Rate Generator is available in
Section 20.7 “Baud Rate Generator”.
SSPSR is the shift register used for shifting data in and
out. SSPBUF provides indirect access to the SSPSR
register. SSPBUF is the buffer register to which data
bytes are written, and from which data bytes are read.
In receive operations, SSPSR and SSPBUF together
create a buffered receiver. When SSPSR receives a
complete byte, it is transferred to SSPBUF and the
SSPIF interrupt is set.
During transmission, the SSPBUF is not buffered. A
write to SSPBUF will write to both SSPBUF and
SSPSR.
20.2.2 SPI MODE OPERATION
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
output time)
• Clock Edge (output data on rising/falling edge of
SCK)
• 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
function, 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
TRIS bit cleared
• SCK (Slave mode) must have corresponding
TRIS bit set
• 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.
2012-2014 Microchip Technology Inc.
DS40001624C-page 179
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