STPM10 datasheet(34/51 Pages) STMICROELECTRONICS

34 / 51 page

Theory of operation

STPM10

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Doc ID 17728 Rev 3

t1 → t2: Latching phase. Interval value > 2/fCLK

t2 → t3: Data latched, SPI idle. Interval value > 30 ns

t3 → t4: Enable SPI for read operation. Interval value > 30 ns

t4 → t5: Serial clock counter is reset. Interval value > 30 ns

t5 → t6: SPI reset and enabled for read operation. Interval value > 30 ns

t7: Internal data transferred to SDA

t8: SDA data is stable and can be read

The system that reads the data record from the STPM10 should check the integrity of each

data record. If the check fails, the reading should be repeated, but this time only the shifting

should be applied. Otherwise, new data would be latched into transmission latches and the

one incorrectly read would be lost.

Normally, each byte is read out as the most significant bit (MSB) first. But this can be

changed by setting the MSBF configuration bit in the STPM10 CFL data record. If this is

done, each byte is read out as the least significant bit (LSB) first.

7.22

Writing procedure

Each writable bit (configuration and mode bits) has its own 6-bit absolute address. For the

configuration bits, the 6-bit address value corresponds to its decimal value, while for the

mode bits the addresses are the ones indicated in Section 7.18: Mode signals.

In order to change the state of a latch, one must send a byte of data to the STPM10, which

is the normal way to send data via SPI. This byte consists of 1-bit data to be latched (MSB),

followed by the 6-bit address of the destination latch, followed by 1-bit don't care data (LSB),

which makes a total of 8 bits of command byte.

For example, if we want to set configuration bit 47 (part of the secondary current channel

calibrator) to 0, we must convert the decimal 47 to its 6-bit binary value: 101111. The byte

command is then composed as follows:

Figure 24.

Timing for data record reading

3t4

SCLNLC

SDATD

SYN

SCS

1st byte

last bit of 32nd byte

f(read)

SCLNLC

SDATD

SYN

SCS

1st byte

last bit of 32nd byte

f(read)

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