IOBUS1 datasheet(39/88 Pages) FTDI

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Datasheet

Vinculum-II Embedded Dual USB Host Controller IC

V ers ion 1 .7

Doc ument N o.: FT _000138 C learance N o.: FT DI# 1 43

6.2 Serial Peripheral Interface – SPI Modes

The Serial Peripheral Interface Bus is an industry standard communications interface. Devices

communicate in Master / Slave mode, with the Master initiating the data transfer.

VNC2 has one master module and two slave modules. Each SPI slave module has four signals – clock,

slave select, MOSI (master out – slave in) and MISO (master in – slave out). The SPI Master has the

same four signals as the slave modules but with one additional signal because it requires a slave select

for the second slave module. Table 6.2 lists how the signals are named in each module.

The SPI Master clock can operate up to one half of the CPU system clock depending on what power mode

the device is set to:



Normal power mode 48Mhz would set the SPI maximum clock to 24Mhz



Low power mode 24Mhz would set the SPI maximum clock to 12Mhz



Lowest power mode 12Mhz would set the SPI maximum clock to 6hMz

Module

Signal Name

Type

Description

SPI Slave

spi_s0_clk

Input

Clock input – slave 0

spi_s0_ss#

Input

Active low chip select input – slave 0

spi_s0_mosi

Input

Master out serial in – slave 0

spi_s0_miso

Output

Master in slave out – slave 0

SPI Slave

spi_s1_clk

Input

Clock input – slave 1

spi_s1_ss#

Input

Active low chip select input – slave 1

spi_s1_mosi

Input

Master out slave in – slave 1

spi_s1_miso

Output

Master in slave out – slave 1

SPI Master

spi_m_clk

Output

Clock output – master

spi_m_mosi

Output

Master out slave in - master

spi_m_miso

Input

Master in slave out - master

spi_m_ss_0#

Output

Active low slave select 0 from master to slave 0

spi_m_ss_1#

Output

Active low slave select 1 from master to slave 1

Table 6.2 SPI Signal Names

The SPI slave protocol by default does not support any form of handshaking . FTDI have added extra

modes to support handshaking, faster throughput of data and reduced pin count. There are 5 modes

(Table 15) of operation in the VNC2 SPI Slave.



Full Duplex – Section 0



Half Duplex, 4 pin - Section 6.3.3



Half Duplex, 3 pin - Section 6.3.4



Unmanaged - Section 6.3.5



VNC1L legacy mode – Section 6.3.6

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