SPI operations

AN2159

8/23

Doc ID 11400 Rev 3

The command byte will be then composed like this: 1 bit DATA value + 6-bits address +1 bit

(0 or 1). In this case the binary command will be 01011111 (0x5F) or 01011110 (0x5E).

The writing procedure timing is shown in Figure 3.

Commands for changing configuration bits and system signals should be sent during active

signals SCS and SYN as it is shown in Figure 3.

The SYN must be put low in order to disable SDA output driver of the device and make the

SDA as an input pin. A string of commands can be send within one period of active signals

SCS and SYN or command can be followed by reading the data record but, in this case, the

SYN should be deactivated in order to enable SDA output driver and a SYN pulse should be

applied before activation of SCS in order to latch the data.

Given the connection between STPMxx and a microcontroller as shown in the previous

paragraph, it is possible to implement the writing procedure in the firmware through the

following steps:

Figure 3.

Timing for writing configuration bits and mode signals

t

2

t

1

t

4

t

3

t

6

t

5

t

8

t

7

t

9

SDA

SCL

SYN

SCS