STPM01 datasheet(34/56 Pages) STMICROELECTRONICS

34 / 56 page

Theory of operation

STPM01

34/56

As it is indicated above, the STPM01 includes 56 CFG bits. Normally, some of these bits

should be permanently set during production of application of STPM01 in order to protect

the application from power fails. Of course, if an application would include an on-board

microcontroller, it could reload the configuration and calibration values after power on restart

and so, the permanent set of STPM01 would not be necessary. But this is not very safe way

to do it, because due to some EMI even imposed to tamper the meter, the microcontroller

may become lost and during such state, it can change some system signals in the STPM01

or somebody can change the calibration and configuration by changing the software of on-

board microcontroller.

8.20

Mode signals

The STPM01 includes 8 Mode signals located in the DFP data record, 3 of these are used

only for internal testing purposes while 5 are useful to change some of the operation of the

STPM01. The mode signals are not retained when the STPM01 supply is not available and

then they are cleared when a POR occurs but they are not cleared when a remote reset

command (RRR) is sent through SPI.

The mode signals bit can be written using the normal writing procedure of the SPI interface

(see SPI section).

Of course, we can clear the RD by clearing all system signals. The first way is to generate

POR signal but this way we clear and reset the whole device. An alternative way is to set the

TSTD bit in the shadow latches. This setting becomes effective after SCS goes to idle state

when the TSTD clears all system signals including itself but, it does not reset the whole

device.

110000

CRC

2-bit unsigned data for calibration of RC oscillator. (see Typical Characteristics

in page 8)

CRC=0, or CRC=3 cal=0%

CRC=1, cal=+10%;

CRC=2, cal=-10%.

110001 49 (1)

110010

NOM

2-bit modifier of nominal voltage for Single Wire Meter.

NOM=0: KNOM=0.3594 / NOM=1: KNOM=0.3906 / NOM=2: KNOM=0.4219 /

NOM=3: KNOM=0.4531;

110011 51 (1)

110100

ADDG

Selection of additional gain on current channels:

ADDG=0: Gain+=0 / ADDG=1: Gain+=8

110101

CRIT

Selection of tamper threshold:

CRIT =0: 12,5% / CRIT =1: 6,25%

110110

LVS

Type of stepper selection:

LVS=0: pulse width 31.25 ms, 5V, / LVS=1: pulse width, 156.25 ms, 3V

110111

Reserved

IMPORTANT: This Bit represents the MSB of the decimal value indicated in the description column.

Table 16.

Configuration bits map

Address

Name

N. of

bits

Description (1)

6-BIT

Binary

DEC

STPM01 数据表(PDF) 34 Page - STMicroelectronics

STPM01 数据表(HTML) 34 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56

数据表下载