AN2159

SPI operations

Doc ID 11400 Rev 3

9/23

1.

disable the SPI peripheral;

2.

set MISO, SCLK and SS to be output;

3.

set the pin which is connected to SYN to be output high;

4.

activate SCS first and then SYN;

5.

activate SCL;

6.

apply a bit value to SDA and deactivate SCL;

7.

repeat the last two steps seven times to complete one byte transfer;

8.

repeat the last three steps for any remaining byte transfer;

9.

deactivate SYN and the SCS;

10. enable again the SPI module;

Note:

For STPM01 only: To temporary set any bit, it is necessary to set the RD system signal

before any other bit. This bit determines the device functioning from OTP shadow latches

and not from OTP memory. The procedure to set this signal is that shown above. For

permanent writing of any bit see next paragraph.

In case of Precharge command (0xFF), emulation above is not necessary, it can be send

before any reading command. In fact, due to the pull up device on the SDA pin the processor

needs to perform the following steps:

1.

activate SYN first in order to latch the results;

2.

after at least 1 µs activate SCS;

3.

write one byte to the transmitter of SPI (this will produce 8 pulses on SCL with SDA=1);

4.

deactivate SYN;

5.

read the data records as shown in paragraph 4.4 (the sequence of reading will be

altered);

6.

deactivate SCS.