RM0352 datasheet(104/138 Pages) STMICROELECTRONICS

104 / 138 page

SPI (serial peripheral interface)

RM0352

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DocID024647 Rev 1

11.4.2

Control register 1, SSPCR1

The SSPCR1 register characteristics are:

Purpose

The SSPCR1 is the control register 1 and contains four different bit

fields, that control various functions within the PrimeCell SSP.

Usage constraints

There are no usage constraints.

Configurations

Available in all SSP configurations.

Attributes

See

Table 96.

Table 98 shows the bit assignments.

11.4.3

Data register, SSPDR

The SSPDR register characteristics are:

Purpose

The SSPDR is the data register and is 16-bit wide. When the SSPDR

is read, the entry in the receive FIFO, pointed to by the current FIFO

read pointer, is accessed. As data values are removed by the

PrimeCell SSP receive logic from the incoming data frame, they are

placed into the entry in the receive FIFO, pointed to by the current

FIFO write pointer.

Table 98. SSPCR1 register bit assignments

Bits

Name

Function

[15:4]

RESERVED, read unpredictable, should be written as 0.

[3]

SOD

Slave-mode output disable. This bit is relevant only in the slave mode, MS = 1. In multiple-slave

systems, it is possible for a PrimeCell SSP master to broadcast a message to all slaves in the

system while ensuring that only one slave drives data onto its serial output line. In such systems

the

RXD lines from multiple slaves could be tied together.

To operate in such systems, the SOD bit can be set if the PrimeCell SSP slave is not supposed

to drive the

SSPTXD line:

SSP can drive the

SSPTXD output in slave mode.

SSP must not drive the

SSPTXD output in slave mode.

[2]

Master or slave mode select.

This bit can be modified only when the PrimeCell SSP is disabled, SSE = 0:

device configured as master, default.

device configured as slave.

[1]

SSE

Synchronous serial port enable:

SSP operation disabled.

SSP operation enabled.

[0]

LBM

Loop back mode:

normal serial port operation enabled.

output of transmit serial shifter is connected to input of receive serial shifter internally.

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