STPM01 datasheet(37/56 Pages) STMICROELECTRONICS

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STPM01

Theory of operation

37/56

8.21.1

Remote Reset

The timing diagram of the operation is shown on the Figure 1. The time step can be as short

as 30ns.

The internal reset signal is named RRR. Unlike the POR, the RRR signal does not cause

the 30ms retard restart of analog module and the 120ms retard restart of digital module.

This signal doesn’t clear the mode signals.

All the time intervals must be longer than 30ns. t7 Æ t8 is the reset time, this interval must be longer than 30ns

as well.

8.22

Reading data records

Data records reading will take place most often when there will be an on-board

microcontroller in an application. Such microcontroller will be able to read all measurement

results and all system signals (configuration, calibration, status, mode). Again, the time step

can be as short as 30ns. There are two phases of reading, called latching and shifting.

Latching is used to sample results into transmission latches. The transmission latches are

the Flip-Flops that hold the data in the SPI interface. This is done with the active pulse on

SYN when SCS is idle. The length of pulse on SYN must be longer than 2 periods of

measurement clock, i.e. more than 500ns at 4MHz.

The shifting starts when SCS become active. In the beginning of this phase another, but

much shorter pulse (30ns) on SYN should be applied in order to ensure that an internal

transmission serial clock counter is reset to zero. An alternative way is to extend the pulse

on SYN into the second phase of reading. After that reset is done, a 32 serial clocks per

data record should be applied. Up to 8 data records can be read this way. This procedure

can be aborted at any time by deactivation of SCS (see figure 23).

The first read out byte of data record is Least Significant Byte (LSB) of data value and of

course, the fourth byte is Most Significant Byte (MSB) of data value. Each byte can be

Figure 23.

Timing for providing remote reset request

SCS

SYN

SCLNLC

SDATD

SCS

SYN

SCLNLC

SDATD

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