L6364 datasheet(22/60 Pages) STMICROELECTRONICS

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8.3.1

Pin functions in transparent mode

In transparent mode, the MOSI and MISO pins are used for both SPI communication, and for the transparent

path. The SS pin controls the use of the MOSI and MISO pins, according to Table 18.

Table 18. Pin dual use in transparent mode

SPI comm’s

Transparent path

MOSI

MISO

SS=’0’

SPI comm’s active

CQ output switch control frozen

SPI data in

SPI data out

SS=’1’

SPI comm’s frozen

Transparent path active

CQ output switch control

Filtered CQ line level

An SPI communication in transparent mode is shown in Figure 9. Initially the L6364 is driving the CQ line; an SPI

exchange is then conducted in which the L6364 is instructed to stop driving the line, and finally the IO-Link master

drives the CQ line.

Typically the microcontroller SPI access routine records the MOSI level in use before setting SS='0' to start an

SPI access, and assert this value again on the MOSI line before setting SS='1'.

The microcontroller should preset the MOSI pin to the required level before the first SPI access enabling

transparent mode.

Support for this may, however, be automatic depending on the microcontroller.

The SPI connection to the L6364 is not suitable for a bus connection of multiple SPI slaves in transparent mode

as the MOSI line is permanently driven.

Figure 9. Illustration of operation in transparent mode

MOSI

MISO

SCK

transparent path in

operation SIO=HS=LS='1'

SPI access

(transparent path frozen)

transparent path in

operation SIO=HS=LS='0'

sampled MOSI used for

transparent path in SPI

MOSI value reasserted

before SS release at end

of SPI comm's

CQ controlled by L6364

CQ controlled by master

8.4

Transparent mode output path

With SS='1', the level of the MOSI pin controls the output switches according to the SIO, HS and LS bit settings

as shown in Table 19. Where SS='0' for SPI access the level latched on the MOSI line is frozen, and used in the

place of the MOSI line itself.

The CCTL:HS and CCTL:LS bits function as enables for the high-side and low-side switches respectively, and

select operation as a high-side, low-side or push-pull device.

Note that the logical path from MOSI to CQ is inverting.

L6364

Transparent mode output path

DS13363 - Rev 4

page 22/60

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