UM0239 datasheet(40/44 Pages) STMICROELECTRONICS

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Communication session examples

UM0239

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8.4

Communication session with Hardware Frame

Synchronization

In this example, the board connected to COM1 is used as the Transmitter while the board

connected to COM3 is the Receiver. Five messages are transmitted across the Mains and

the receiving method is synchronized by ST7540 through the Header Recognition function

of the Control Register. This enables incoming data from the ST7540 to arrive already

synchronized to

EVALCOMMBOARD and are directly sent to the PC.

Actions to perform on GUI connected with COM3:

Click REG on toolbar to open the Control Register parameter dialog box.

–Enable Extended Register.

–Enable Header Recognition.

–Enable Frame Length Count.

–Set Header Length Control to "16 bits".

–Set Frame Header Control to "9B58" (hexadecimal value).

–Set Frame Length Control to "14" (hexadecimal value equal to twenty 16-bit

words or 40 bytes).

–

Click Write CTRL Register.

Click Rx on toolbar to open the Rx Monitor dialog box.

–Set Frame Sync to OFF.

–Set Force Sens. to BU Level to OFF.

–

Click ON.

Actions to perform on GUI connected with COM1:

Click Tx on toolbar to open the Tx Monitor dialog box.

Write the preamble "AAAAAAAA" in the hexadecimal textbox.

Add the header "9B58" in the hexadecimal textbox.

Add the text string "transmission with ST7540 synchronization" (length = 40 bytes) in

the ASCII textbox.

Select Sequence Mode and set Nr. to “5”.

Click ON.

Five messages are transmitted.

Using the Hardware Frame Synchronization feature, the user ensures that the transmitted

bytes always arrive synchronized to the PC as shown in Figure 26.

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