SPI operations

AN3254

6/24

Doc ID 17783 Rev 1

3

SPI operations

3.1

Remote reset request

The STPMC1 has no reset pin. It is automatically reset by the power on reset (POR) circuit

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

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

microprocessor when a malfunction of the metering device has been detected.

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

module and the 120 ms retarded restart of the digital module. This reset does not clear the

mode signals.

Note:

also be longer than 30 ns.

3.2

Data registers writing

Each writable bit (configuration and mode signals bits) of the STPMC1 has its own 7-bit

absolute address (see the STPMC1 datasheet for configuration bits map).

In order to change the state of some pins, a byte of data via the SPI must be sent to the

device. This byte consists of 1-bit data to be written (MSB), followed by a 7-bit address of

the destination bit, which makes a command byte.

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