STPM10 datasheet(31/47 Pages) STMICROELECTRONICS

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STPM10

Theory of operation

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7.18

Mode signals

The STPM10 includes 8 mode signals located in the DFP data record. 3 out of these are

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

STPM10. The mode signals are not retained when the STPM10 supply is not available and

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, in the following section.

Table 12: Mode signal description

Bit

Signal

name

Bit value

Status

Binary

command

Hex

command

Bank

Used for RC start-up procedure

0111000x

70 or 71

1111000x

F0 or F1

Reserved

CSEL

Current channel 1 selected when

tamper is disabled

0111 100x

78 or 79

Current channel 2 selected when

tamper is disabled

1111 100x

F8 or F9

Reserved

Pre-charge

Swap the 32-bit data record

readings. From 1,2,3,4,5,6,7,8, to

5,6,7,8,1,2,3,4 and vice-versa

1111111x

CSEL: in normal operation, if the anti-tamper module is not activated, the STPM10 selects

channel 1 as the source of current information. For debug or calibration purposes it is

possible to select channel 2 as the source of the current channel signal when the tamper

module is disabled. This is done by setting the CSEL mode bit.

Pre-charge: this command swaps the sequence of data records read, allowing the reading

of the last four data records first, and the first four second. The reading sequence is 5, 6, 7,

8, 1, 2, 3, 4. Unlike the other mode signals, the pre-charge command is not retained inside

the STPM10, but should be sent each time before the reading of the data records.

BANK: it is used to activate RC oscillator (as indicated in Section 7.11.1: "RC start-up

procedure").

7.19

SPI interface

The SPI interface supports a simple serial protocol, which is implemented to enable

communication of some master system (microcontroller or PC) and the device. Three tasks

can be performed with this interface:



Remote resetting of the device



Reading data records



Writing the mode bits and the configuration bits

Four pins of the device are dedicated to this purpose: SCS, SYN, SCL and SDA. SCS,

SYN and SCL are all input pins, while SDA can be input or output according to whether the

SPI is in write or read mode. A high level signal for these pins means a voltage level higher

than 0.75 x VCC, while a low level signal means a voltage value lower than 0.25 x VCC.

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