P89CV51RB2FBC datasheet(39/73 Pages) NXP

39 / 73 page

P89CV51RB2_RC2_RD2_1

Product data sheet

Rev. 01 — 5 October 2007

39 of 73

NXP Semiconductors

P89CV51RB2/RC2/RD2

80C51 with 1 kB RAM, SPI

6.7 Serial Peripheral Interface (SPI)

6.7.1 SPI features

• Master or slave operation

• 10 MHz bit frequency (max)

• LSB ﬁrst or MSB ﬁrst data transfer

• Four programmable bit rates

• End of transmission (SPIF)

• Write-collision ﬂag protection (WCOL)

• Wake-up from Idle mode (Slave mode only)

6.7.2 SPI description

The serial peripheral interface allows high-speed synchronous data transfer between the

P89CV51RB2/RC2/RD2 and peripheral devices or between several

P89CV51RB2/RC2/RD2 devices. Figure 16 shows the correspondence between master

and slave SPI devices. The SPICLK pin is the clock output and input for the Master and

Slave modes, respectively. The SPI clock generator will start following a write to the

master devices SPI data register. The written data is then shifted out of the MOSI pin of

the master device into the MOSI pin of the slave device. Following a complete

transmission of one byte of data, the SPI clock generator is stopped and the SPI interrupt

Flag (SPIF) is set. An SPI interrupt request will be generated if the SPI Interrupt Enable bit

(SPIE) and the SPI interrupt enable bit, ES, are both set.

An external master drives the Slave Select input pin (SS) LOW to select the SPI module

as a slave. If SS has not been driven LOW, then the slave SPI unit is not active and the

MOSI pin can also be used as an input port pin.

CPHA and CPOL control the phase and polarity of the SPI clock (SCK). Figure 17 and

Figure 18 show the four possible combinations of these two bits.

Fig 16. SPI master-slave interconnection

002aaa528

8-BIT SHIFT REGISTER

MSB master LSB

SPI

CLOCK GENERATOR

MISO

MOSI

SCK

8-BIT SHIFT REGISTER

MSB slave LSB

VSS

VDD

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