AN2159

SPI operations

Doc ID 11400 Rev 3

7/23

4

SPI operations

4.1

Remote reset request

STPM01 and STPM10 have no reset pin. They are automatically reset by the power on

the SPI interface giving a dedicated command, which timing diagram is shown in Figure 2.

The reset through SPI (remote reset request - RRR) is sent from the on-board

microprocessor when some malfunction of metering device has been detected.

Unlike the POR, the RRR signal does not cause the 30 ms retarded restart of analog

module and the 120 ms retarded restart of digital module. This reset doesn't clear the mode

signals.

Note:

be longer than 30 ns as well.

4.2

Data registers writing

Each writable bit (configuration and mode signals bits) of STPM01 and STPM10 has its own

6-bit absolute address (see related datasheets for configuration bits map).

In order to change the state of some pin one must send to STPM01 a byte of data via SPI.

This byte consists of 1-bit data to be written (MSB), followed by 6-bit address of destination

bit, followed by 1-bit don't care data (LSB), which makes a command byte.

For example, to set the STPM01 configuration bit 47 (part of the secondary current channel

calibrator) to 0, the decimal 47 should be first converted to its 6-bit binary value: 101111.

Figure 2.

Remote reset request timing

t

10

t

2

t

1

t

4

t

3

t

6

t

5

t

8

t

7

t

9

SDA

SCL

SYN

SCS