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.
CPU clock
DIVIDER
BY 4, 16, 64, 128
SELECT
SPI clock (master)
SPI CONTROL
MSTR
SPEN
8-BIT SHIFT REGISTER
READ DATA BUFFER
clock
CLOCK LOGIC
S
M
M
S
PIN
CONTROL
LOGIC
S
M
MISO
P2.3
MOSI
P2.2
SPICLK
P2.5
SS
P2.4
SPI STATUS REGISTER
SPI
interrupt
request
Fig 15. SPI block diagram
SPI CONTROL REGISTER
internal
data
bus
002aaa900
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.
P89LPC9321_1
Product data sheet
Rev. 01 — 9 December 2008
© NXP B.V. 2008. All rights reserved.
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