NXP Semiconductors P89LPC9321 UM10310, User Manual

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User manual Rev. 01 — 1 December 2008 88 of 139
NXP Semiconductors
UM10310
P89LPC9321 User manual
In Figure 41 , SSIG (SPCTL.7) bits for the slaves are logic 0, and the slaves are selected
by the corresponding SS signals. The SPI master can use any port pin (including
P2.4/SS) to drive the SS pins.
12.1 Configuring the SPI
Table 82 shows configuration for the master/slave modes as well as usages and
directions for the modes.
Fig 41. SPI single master multiple slaves configuration.
002aaa903
master slave
8-BIT SHIFT
REGISTER
SPI CLOCK
GENERATOR
8-BIT SHIFT
REGISTER
MISO
MOSI
SPICLK
port
port
MISO
MOSI
SPICLK
SS
slave
8-BIT SHIFT
REGISTER
MISO
MOSI
SPICLK
SS
Table 82. SPI master and slave selection
SPEN SSIG SS Pin MSTR Master
or Slave
Mode MISO MOSI SPICLK Remarks
0 x P2.4
[1]
x SPI
Disabled P2.3
[1]
P2.2
[1]
P2.5
[1]
SPI disabled. P2.2, P2.3, P2.4, P2.5 are used
as port pins.
1 0 0 0 Slave output input input Selected as slave.
1 0 1 0 Slave Hi-Z input input Not selected. MISO is high-impedance to avoid
bus contention.
1 0 0 1 (->
0)
[2]
Slave output input input P2.4/SS is configured as an input or
quasi-bidirectional pin. SSIG is 0. Selected
externally as slave if SS is selected and is
driven low. The MSTR bit will be cleared to
logic 0 when SS becomes low.