UM10310_1 © NXP B.V. 2008. All rights reserved.
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

Tabl e 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
0xP2.4
[1] xSPI
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.
1001 (->
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.