P89LPC9321 datasheet(40/70 Pages) NXP

40 / 70 page

P89LPC9321_1

Product data sheet

Rev. 01 — 9 December 2008

40 of 70

NXP Semiconductors

P89LPC9321

8-bit microcontroller with accelerated two-clock 80C51 core

7.25 SPI

The P89LPC9321 provides another high-speed serial communication interface: the SPI

interface. SPI is a full-duplex, high-speed, synchronous communication bus with two

operation modes: Master mode and Slave mode. Up to 3 Mbit/s can be supported in either

Master mode or Slave mode. It has a Transfer Completion Flag and Write Collision Flag

Protection.

The SPI interface has four pins: SPICLK, MOSI, MISO and SS:

• SPICLK, MOSI and MISO are typically tied together between two or more SPI

devices. Data ﬂows from master to slave on MOSI (Master Out Slave In) pin and ﬂows

from slave to master on MISO (Master In Slave Out) pin. The SPICLK signal is output

in the Master mode and is input in the Slave mode. If the SPI system is disabled, i.e.,

SPEN (SPCTL.6) = 0 (reset value), these pins are conﬁgured for port functions.

• SS is the optional slave select pin. In a typical conﬁguration, an SPI master asserts

one of its port pins to select one SPI device as the current slave. An SPI slave device

uses its SS pin to determine whether it is selected.

Typical connections are shown in Figure 16 through Figure 18.

Fig 15. SPI block diagram

002aaa900

CPU clock

DIVIDER

BY 4, 16, 64, 128

SELECT

CLOCK LOGIC

SPI CONTROL REGISTER

READ DATA BUFFER

8-BIT SHIFT REGISTER

SPI CONTROL

SPI STATUS REGISTER

SPI clock (master)

CONTROL

LOGIC

MISO

P2.3

MOSI

P2.2

SPICLK

P2.5

P2.4

SPI

interrupt

request

internal

data

bus

MSTR

SPEN

clock

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