UM0934 datasheet(22/113 Pages) STMICROELECTRONICS

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MAC layer

UM0934

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Doc ID 17389 Rev 2

MAC layer

4.1

Overview

The ST7570 embeds a MAC layer compliant with [2], with additional functions for the

electrical delta-phase measurement.

In order to meet the application’s functions and physical channel characteristics, many

parameters involved at this layer can be programmed by the user.

4.2

Operating modes

The following operating modes are supported, as defined by [2]:

●

Client: is the master of the communication.

●

Server: is the slave of the communication. Before being allowed to transmit, the

ST7570 modem needs to achieve the “slot synchronization”.

4.2.1

Additional operating mode

In addition to the operating modes (Client and Server), defined by [2], the MAC layer of the

ST7570 also embeds a Monitor mode for specific tasks.

Monitor mode

When the node is running as “Monitor”:

●

All the time-outs (Section 4.7) are disabled to allow the reception of frames, even if they

are not valid (i.e. invalid FCS) or after a long silence period

●

Every received frame causes an CMD_SynchroIndication (Section 5.3.1) to be sent to

the host

●

All the valid frames (i.e. valid FCS) are notified through an CMD_DataIndication

(Section 5.3.11), whatever the source address and destination address

●

Each repetition is notified through an CMD_DataIndication (Section 5.3.11)

independently, if the modem is set as well as a REPEATER (Section 4.8.5).

Special MIB objects (disable frame type check and disable CRC check, 0008h

Section 6.5.9

, and auto synchro reject 0015h, Section 6.5.22) let the Monitor be configured

as a sniffer capable of receiving and notifying all the frames:

●

Disable frame type check and disable CRC check: these flags allow the long MAC

frame type and frame CRC check to be disabled so that the wrong MAC frames are

notified

●

Auto synchro reject: this parameter makes the Monitor able to automatically reject the

synchronism at the end of each received MAC frame.

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