le79128 Zarlink Semiconductor, le79128 Datasheet - Page 36

• Manufacturer Part Number: le79128
• Description: Next Generation Voiceedge™ Control Processor Next Generation Carrier Chipset Ngcc
• Manufacturer: Zarlink Semiconductor

Serial Peripheral Interface (SPI)
Serial Peripheral Interface (SPI) is a physical interface of the VCP device used by the external host to communicate with the
device. The SPI interface is compatible with the SPI interface used by general DSPs, so that those chips can interface with the
VCP device without any glue logic. Because the SPI has the same logical view as the General Purpose Parallel Interface (GPI),
the host can issue the same commands or data to the VCP device regardless of the physical interface.
SPI External Pins Connection
The SPI is a 4-wire synchronized serial interface used in many DSPs and microcontrollers. The data is transferred bi-directional
from master to slave and from slave to master. The master provides clock SCK to synchronize the data transfer, and the signals
MOSI and MISO are for the data bit stream. SPI master can be a 3-wire or 4-wire SPI master, depending on if the master drives
the SS signal. A 4-wire SPI master pulls SS Low when transferring data. In a single master/slave pair the master can be a 3-wire
interface, with the SS pin at the slave tied Low.
The VCP device will be the SPI slave, and the external host will be the SPI master. Signal MOSI will connect to the SI pin and
signal MISO will connect to the SO pin of the VCP device. Microsemi VCP devices sample the input signal SI on the rising edge
of the clock and change the output signal SO on the falling edge of the clock.
Figure 15
pin, a 3-wire interface as shown in
SCK
MOSI
MISO
SS
Signal Name
Table 17. SPI Signals
shows the SPI interface system with a 4-wire SPI master. When the VCP device supports command framing on the SS
Input
Input
Output
Input
Type
Le79128 VCP
Figure 16, on page 37
Figure 15. 4-Wire Master-Slave Connections
SPI clock
SPI slave input/master output
SPI slave output/master input
SPI Slave select low
Microsemi Corporation - CMPG
Slave
SPI
Le79128
can be utilized.
SCK
SS
SO
SI
36
Description
MOSI
MISO
SCK
SS
SCK
MOSI
MISO
SS
Preliminary Data Sheet
Master
SPI