LPC2917 datasheet(28/68 Pages) PHILIPS

28 / 68 page

LPC2917_19_1

Preliminary data sheet

Rev. 1.01 — 15 November 2007

28 of 68

NXP Semiconductors

LPC2917/19

ARM9 microcontroller with CAN and LIN

Depending on the operating mode selected, the SPI_CS_OUT outputs operate as an

active-HIGH frame synchronization output for Texas Instruments synchronous serial

frame format or an active-LOW chip select for SPI.

Each data frame is between four and 16 bits long, depending on the size of words

programmed, and is transmitted starting with the MSB.

There are two basic frame types that can be selected:

• Texas Instruments synchronous serial

• Motorola Serial Peripheral Interface

8.4.5.3

Modes of operation

The SPI module can operate in:

• Master mode:

– Normal transmission mode

– Sequential slave mode

• Slave mode

8.4.5.4

SPI pin description

The three SPI modules in the LPC2917/19 have the pins listed below. The pins are

combined with other functions on the port pins of the LPC2917/19, see Section 8.3.3.

Table 16 shows the SPI pins (x runs from 0 to 2; y runs from 0 to 3).

[1]

Direction of SPIx SCS and SPIx SCK pins depends on master or slave mode. These pins are output in

master mode, input in slave mode.

[2]

In slave mode there is only one chip-select input pin, SPIx SCS0. The other chip selects have no function in

slave mode.

8.4.5.5

SPI clock description

The SPI modules are clocked by two different clocks; CLK_SYS_PESS and CLK_SPIx (x

= 0-2), see Section 7.2.2. Note that each SPI has its own CLK_SPIx branch clock for

power management. The frequency of all clocks CLK_SPIx is identical as they are derived

from the same base clock BASE_CLK_SPI. The register interface towards the system bus

is clocked by CLK_SYS_PESS. The serial-clock rate divisor is clocked by CLK_SPIx.

The SPI clock frequency can be controlled by the CGU. In master mode the SPI clock

frequency (CLK_SPIx) must be set to at least twice the SPI serial clock rate on the

interface. In slave mode CLK_SPIx must be set to four times the SPI serial clock rate on

the interface.

Table 16.

SPI pins

Symbol

Direction

Description

SPIx SCSy

in/out

SPIx chip select[1][2]

SPIx SCK

in/out

SPIx clock[1]

SPIx SDI

SPIx data input

SPIx SDO

out

SPIx data output

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