NXP Semiconductors LPC24XX UM10237 - Manual (Page 537)

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User manual Rev. 04 — 26 August 2009 537 of 792
NXP Semiconductors
UM10237
Chapter 20: LPC24XX SSP interface SSP0/1
4. Pin descriptions
5. Bus description
5.1 Texas Instruments synchronous serial frame format
Figure 20–96 shows the 4-wire Texas Instruments synchronous serial frame format
supported by the SSP module.
Table 469. SSP pin descriptions
Pin
Name
Type
Interface pin
name/function
Pin Description
SPI SSI Microwire
SCK0/1 I/O SCK CLK SK Serial Clock. SCK/CLK/SK is a clock signal used
to synchronize the transfer of data. It is driven by
the master and received by the slave. When SPI
interface is used the clock is programmable to be
active high or active low, otherwise it is always
active high. SCK1 only switches during a data
transfer. Any other time, the SSPn either holds it in
its inactive state, or does not drive it (leaves it in
high impedance state).
SSEL0/1 I/O SSEL FS CS Frame Sync/Slave Select. When the SSPn is a
bus master, it drives this signal from shortly before
the start of serial data, to shortly after the end of
serial data, to signify a data transfer as appropriate
for the selected bus and mode. When the SSPn is a
bus slave, this signal qualifies the presence of data
from the Master, according to the protocol in use.
When there is just one bus master and one bus
slave, the Frame Sync or Slave Select signal from
the Master can be connected directly to the slave’s
corresponding input. When there is more than one
slave on the bus, further qualification of their Frame
Select/Slave Select inputs will typically be
necessary to prevent more than one slave from
responding to a transfer.
MISO0/1 I/O MISO DR(M)
DX(S)
SI(M)
SO(S) Master In Slave Out. The MISO signal transfers
serial data from the slave to the master. When the
SSPn is a slave, serial data is output on this signal.
When the SSPn is a master, it clocks in serial data
from this signal. When the SSPn is a slave and is
not selected by FS/SSEL, it does not drive this
signal (leaves it in high impedance state).
MOSI0/1 I/O MOSI DX(M)
DR(S)
SO(M)
SI(S) Master Out Slave In. The MOSI signal transfers
serial data from the master to the slave. When the
SSPn is a master, it outputs serial data on this
signal. When the SSPn is a slave, it clocks in serial
data from this signal.