UM0239 datasheet(34/44 Pages) STMICROELECTRONICS

34 / 44 page

Ping sessions

UM0239

34/44

7.4

Ping session flowcharts

Figure 19 and Figure 20 describe the Master and the Slave loops, respectively, while a ping

session is in progress.

Figure 19.

Ping master loop

Ping Start

Transmit

MSG (0)

MAC enable ?

YES

SLAVE ADD = 1

MSG_NUM= 0

Slave Add. <

Slave No.?

Slave add. ‡ 1

Ping Master settings:

•MASTER ADDRESS

•SLAVE NUM

•TOT MESSAGE NUM

•WAIT TIME

•MAC (MEDIUM ACCESS CONTROL)

•MAX WAIT SLOT NR.

•MAX WAIT TIME

•REPETITION

YES

MSG_NUM ‡ 1

Ping Master current message output data:

•OK MESS.

•CORR. MESS.

•KO MESS.

•WRONG FCS MESS.

•NOT ACK MESS.

YES

Calculate FCS

YES

OK MESS.

YES

Create MSG (0)

SLAVE ADD‡ 1

YES

Create MSG

(MSG_NUM)

YES

CORR MESS.

WRONG

FCS MESS.

YES

MSG NOT ACK

YES

Ping Stop

MAC equal to

PD and Control

to CD?

Set Control

Line busy

and Max Wait Time

not elapsed?

Wait RAND time

(from 1 to Max

Wait Slot No. * 4 ms)

MSG_NUM <

TOT MSG NUM?

Repetition

enabled and

< 3 messages

transmitted?

MAC enable ?

Transmit MSG

(MSG_NUM)

Message

Acknowledged

and Wait Time

not elapsed?

Master Address

correct ?

Repetition

enabled and

< 3 messages

transmitted?

FCS

calculated equal

to FCS

received?

Use FEC and

calculate a

new FCS

New FCS

equal to FCS

of corrected

message?

Line busy

and Max Wait Time

not elapsed?

Wait RAND time

(from 1 to Max

Wait Slot No. * 4 ms)

Slave Add. <

Slave No.?

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