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12.2.9 Mode fault
The SSEL signal must always be inactive when the SPI block is a master. If the SSEL
signal goes active, when the SPI block is a master, this indicates another master has
selected the device to be a slave. This condition is known as a mode fault. When a mode
fault is detected, the mode fault (MODF) bit in the status register will be activated, the SPI
signal drivers will be de-activated, and the SPI mode will be changed to be a slave.
12.2.10 Slave abort
A slave transfer is considered to be aborted, if the SSEL signal goes inactive before the
transfer is complete. In the event of a slave abort, the transmit and receive data for the
transfer that was in progress are lost, and the slave abort (ABRT) bit in the status register
will be activated.
12.3 Pin description
Table 139: SPI pin description
Pin Name
Type
SCK0
Input/Output
SSEL0
Input
MISO0
Input/Output
MOSI0
Input/Output
12.4 Register description
The SPI contains 5 registers as shown in
word accessible.
User manual
Pin Description
Serial Clock. The SPI is a clock signal used to synchronize the transfer of data across the
SPI interface. The SPI is always driven by the master and received by the slave. The clock is
programmable to be active HIGH or active LOW. The SPI is only active during a data transfer.
Any other time, it is either in its inactive state, or tri-stated.
Slave Select. The SPI slave select signal is an active LOW signal that indicates which slave
is currently selected to participate in a data transfer. Each slave has its own unique slave
select signal input. The SSEL must be LOW before data transactions begin and normally
stays LOW for the duration of the transaction. If the SSEL signal goes HIGH any time during
a data transfer, the transfer is considered to be aborted. In this event, the slave returns to
idle, and any data that was received is thrown away. There are no other indications of this
exception. This signal is not directly driven by the master. It could be driven by a simple
general purpose I/O under software control.
On the LPC2101/02/03 the SSEL0 pin can be used for a different function when the
SPI0 interface is only used in Master mode. For example, the pin hosting the SSEL0
function can be configured as an output digital GPIO pin or used to select one of the
Match outputs.
Master In Slave Out. The MISO signal is a unidirectional signal used to transfer serial data
from the slave to the master. When a device is a slave, serial data is output on this signal.
When a device is a master, serial data is input on this signal. When a slave device is not
selected, the slave drives the signal high impedance.
Master Out Slave In. The MOSI signal is a unidirectional signal used to transfer serial data
from the master to the slave. When a device is a master, serial data is output on this signal.
When a device is a slave, serial data is input on this signal.
Rev. 01 — 12 January 2006
Table
140. All registers are byte, half word and
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
UM10161
Chapter 12: SPI
161
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