STPM10 datasheet(34/47 Pages) STMICROELECTRONICS

34 / 47 page

Theory of operation

STPM10

34/47

DocID17728 Rev 5

Figure 24: Timing for data record reading

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 the shifting should be

applied this time only. Otherwise, new data are latched into transmission latches and the

one incorrectly read is 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. In this manner 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.

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

while for mode bits, see Section 7.18: "Mode signals". In order to change the state of a

latch, a byte of data must be sent 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; do not care LSB data, 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 of the following: 1-bit data value+6-bits

address+1-bit (0 or 1) as depicted in the figure below. In this case the binary command is

01011111 (0x5F), which is the one depicted, or 01011110 (0x5E):

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