PIC32MX440F256H-80I Datasheet, PDF (392/646 Pages) Microchip Technology – 64/100-Pin General Purpose and USB 32-Bit Flash Microcontrollers

PIC32MX3XX/4XX
17.2 Master and Slave Modes
The PIC32MX3XX/4XX SPI module operates in normal
Master or Slave modes and offers the following addi-
tional modes:
• Framed Master
• Framed Slave
• 8, 16, 32-bit Data Width Transfers
• Slave Select (Slave mode only)
Below is a typical system Master – Slave connection
diagram.
17.2.1 8, 16, AND 32-BIT OPERATION
The PIC32MX3XX/4XX SPI module allows three types
of data widths when transmitting and receiving data
over an SPI bus. The selection of data width deter-
mines the minimum length of SPI data.
Two control bits, MODE32 and MODE16
(SPIxCON<11:10>), define the mode of operation. To
change the mode of operation on the fly, the SPI mod-
ule must be idle, i.e., not performing any transactions.
If the SPI module is switched off (SPIxCON<15> = 0),
the new mode will be available when the module is
again switched on.
The number of clock pulses at the SCKx pin are depen-
dent on the selected mode of operation. For 8-bit mode,
8 clocks; for 16-bit mode, 16 clocks; and for 32-bit mode,
32 clocks are required.
FIGURE 17-2:
SPI MASTER/SLAVE CONNECTION
PIC32MX3XX/4XX
[SPI Master]
Serial Receive Buffer
(SPIxRXB)⁽²⁾
SDOx
PROCESSOR 2
[SPI Slave]
SDIx
Serial Receive Buffer
(SPIxRXB)
Shift Register
(SPIxSR)
MSB
LSB
SDIx
SDOx
Shift Register
(SPIxSR)
MSB
LSB
Serial Transmit Buffer
(SPIxTXB)⁽²⁾
Serial Transmit Buffer
(SPIxTXB)
SPI Buffer
(SPIxBUF)
Serial Clock
SCKx
GPIO/SSx _.
MSTEN (SPIxCON<5>) = 1
SCKx
SSx⁽¹⁾
SPI Buffer
(SPIxBUF)
SSEN (SPIxCON<7>) = 1 and
MSTEN (SPIxCON<5>) = 0
Note 1: Using the SSx pin in Slave mode of operation is optional.
2: User must write transmit data to SPIxBUF and read received data from SPIxBUF. The SPIxTXB and SPIxRXB
registers are memory mapped to SPIxBUF.
DS61143E-page 390
Preliminary
© 2008 Microchip Technology Inc.