DSPIC30F2012AT20ESLASHSP datasheet(91/205 Pages) MICROCHIP

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DS70139E-page 89

dsPIC30F2011/2012/3012/3013

13.0

SPI MODULE

The Serial Peripheral Interface (SPI) module is a syn-

chronous serial interface. It is useful for communicating

with other peripheral devices, such as EEPROMs, shift

registers, display drivers and A/D converters, or other

microcontrollers. It is compatible with Motorola's SPI

and SIOP interfaces. The dsPIC30F2011/2012/3012/

3013 devices feature one SPI module, SPI1.

13.1

Operating Function Description

Figure 13-1 is a simplified block diagram of the SPI

module, which consists of a 16-bit shift register,

SPI1SR , used for shifting data in and out, and a buffer

shown) configures the module. Additionally, status reg-

ister SPI1STAT (not shown) indicates various status

conditions.

Four I/O pins comprise the serial interface:

• SDI1 (serial data input)

• SDO1 (serial data output)

• SCK1 (shift clock input or output)

• SS1 (active-low slave select).

In Master mode operation, SCK1 is a clock output. In

Slave mode, it is a clock input.

A series of eight (8) or sixteen (16) clock pulses shift

out bits from the SPI1SR to SDO1 pin and simulta-

neously shift in data from SDI1 pin. An interrupt is

generated when the transfer is complete and the

interrupt flag bit (SPI1IF) is set. This interrupt can be

disabled through the interrupt enable bit, SPI1IE.

The receive operation is double-buffered. When a com-

plete byte is received, it is transferred from SPI1SR to

SPI1BUF.

If the receive buffer is full when new data is being trans-

ferred from SPI1SR to SPI1BUF, the module will set the

SPIROV bit indicating an overflow condition. The trans-

fer of the data from SPI1SR to SPI1BUF is not com-

pleted and the new data is lost. The module will not

respond to SCL transitions while SPIROV is ‘1’, effec-

tively disabling the module until SPI1BUF is read by

user software.

Transmit writes are also double-buffered. The user

writes to SPI1BUF. When the master or slave transfer

is completed, the contents of the shift register

(SPI1SR) are moved to the receive buffer. If any trans-

mit data has been written to the buffer register, the con-

tents of the transmit buffer are moved to SPI1SR. The

received data is thus placed in SPI1BUF and the trans-

mit data in SPI1SR is ready for the next transfer.

FIGURE 13-1:

SPI BLOCK DIAGRAM

Note: This data sheet summarizes features of this group

of dsPIC30F devices and is not intended to be a complete

reference source. For more information on the CPU,

peripherals, register descriptions and general device

functionality, refer to the “dsPIC30F Family Reference

Manual “ (DS70046).

Note:

See “dsPIC30F Family Reference Man-

ual” (DS70046) for detailed information on

the control and status registers.

Note:

Both the transmit buffer (SPI1TXB) and

the receive buffer (SPI1RXB) are mapped

to the same register address, SPI1BUF.

Read

Write

Internal

Data Bus

SDI1

SDO1

SS1

SCK1

SPI1SR

SPIxBUF

bit 0

Shift

Clock

Edge

Select

FCY

Primary

1, 4, 16, 64

Enable Master Clock

Prescaler

Secondary

Prescaler

1:1 – 1:8

SS & FSYNC

Control

Clock

Control

Transmit

SPIxBUF

Receive

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