L9788 datasheet(185/264 Pages) STMICROELECTRONICS

185 / 264 page

DS12308 Rev 4

185/264

L9788

Micro second channel (MSC) interface

263

Figure 87. MSC upstream commands example

18.4

Micro Second Channel activity watchdog

MSC data frames are monitored to be sent in intervals shorter than tMSC_mon. If L9788

receives no valid data frame for longer than tMSC_mon, it will switch off all the drivers,

removing driver enable command, and the error flag (TRANS_F) is set to 1 and internal

signal "OUT_DIS" will be set to "0". Note: OUT_DIS = driver_en (Read11 frame 1);

tMSC_mon is the time needed to send OUT_DIS, it is different from time needed to turn off

drivers (which can be different depending on driver type, the maximum time to turn off all

drivers is about 300 µs).

To enable again the outputs, the µC has to read the TRANS_F and then send the command

Enable_Driver, and then outputs are reactivated with the first correct data frame. If the fault

flag is not cleared the Enable_Driver command is ignored.

By default the Micro Second Channel activity watch dog is enabled and the monitoring time

will start after writing of the internal signal OUT_DIS bit by Enable_Driver command. Each

time L9788 receives a valid data frame the tMSC_on timer is reset. This means that micro

controller can drive the outputs only when the monitoring module is active.

It is also possible to enable /disable the Micro Second Channel activity watch dog through

MSC_ACT_EN bit (CONFIG_REG2 D0), 0= disable and 1 = enable (reset value).

Read command 1: 1-101010-101010101

Read command 2: 1-101010-010101010

Read command 3: 1-010101-011001100

End Frame1 = 0-0101-10101010-Pb-

End Frame2 = 0-0101-01010101-Pb-

End Frame3 = 0-1010-01100110-Pb-

End Frame4 = 0-1010-11010101-Pb-

End Frame5 = 0-0010-01110111-Pb-

End Frame6 = 0-0010-10101110-Pb-

Inverted read C0-C3 bits

Read D0-D8 bits

Down stream

First

frame

Last

frame

Interframe

D0-D8 => read frames data

C0-C5

16 Frames + end

Read

Up stream

GADG1312161244PS

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