Multitech MMCModem GPRS (MTMMC-G) Manual de usuario descargar pdf (Pagina 27)

Chapter 4 – Data Exchange for Protocol Services

Multi-Tech Systems, Inc. IP Connectivity AT Commands for GPRS-F4 Wireless Modems (PN S000437C) 27

Socket Data Exchange +WIPDATA Continued

[DLE] Escaping Mechanism

A [DLE] character will be sent as data only when it is preceded by another [DLE] character. A single

[DLE] character which is not preceded by a [DLE] character will not be transmitted.

The following schematic explains how [DLE] characters, which have a special meaning in WIPSoft,

are handled on the Wavecom Wireless CPU

On the transmitting side: When a [DLE] character is not escaped (use case: Desktop PC1 sends

data to the Wavecom Wireless CPU

and the data contains a non-escaped [DLE] (<=> no [DLE]

[DLE] sequence), then the [DLE] is not transmitted.

On the transmitting side: When a [DLE] is escaped (use case: Desktop PC1 sends data to the

Wavecom Wireless CPU

and the data contains an escaped [DLE] (<=> [DLE] [DLE] sequence), then

the [DLE] data is transmitted.

On the receiving side: (Use case: When the Desktop PC2 sends data to the Wavecom Wireless

CPU

and the data contains a no escaped [DLE], the data sent from Wireless CPU

to Desktop PC1

will contain an escaped [DLE] preceding the [DLE] character (Desktop PC1 receives a [DLE][DLE]

character from the Wireless CPU).

This scenario is the same for both TCP and UDP sockets.

Protocol Mapped UART IP Network (active socket)

UDP Data containing [DLE][DLE] sequence. Data containing [DLE].

UDP [DLE] alone. A single [DLE] is ignored.

TCP Data containing [DLE][DLE] sequence. Data containing [DLE].

TCP [DLE] alone. A single [DLE] is ignored.

Continuous Transparent Mode

TCP Sockets in Continuous Transparent Mode

In this mode there is no special meaning associated for [DLE]/[ETX] characters. They are considered

as normal data and all the data will be transmitted on the mapped UART.

UDP sockets do not support this mode. Attempting to map an UART in this mode will result in a

“+CME ERROR: 837”.

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Multitech MMCModem GPRS (MTMMC-G) Manual de usuario Pagina 27