Fax Class 1 AT Commands

When the modem transfers data to the DTE, the DTE must filter the data stream by removing all character pairs beginning with <DLE>. The DTE also must recognize <DLE><ETX> as the stream terminator. Upon detecting <DLE><DLE>, the DTE must reinsert a single <DLE> in its place. The modem buffers up to 512 bytes of fax data received from the remote modem if the DTE cannot read the data immediately (AT+FRM command).

For the AT+FTH and AT+FRH commands, data is sent and received using HDLC formatting. The format for HDLC framing is provided below. When sending the HDLC data, the modem automatically generates the flags and the frame checking sequence (Frame Check Sum). All the other fields are transmitted to or received from the DTE (that is, these fields are under the control of the DTE).

Figure 8. T.30 HDLC Frame Format

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Facsimile

Facsimile

Frame

 

 

 

 

 

Address

Control

Checking

 

 

 

Flag

Flag

Control

Information

Flag

 

 

Field

Field

Sequence

 

 

 

 

Field

Field

 

 

 

 

 

 

 

(FCS)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

After receiving a frame correctly using the AT+FRH command (FCS is OK), the DCE returns an ‘OK’ message to the DTE. If the frame is received in error (FCS is not OK, carrier is lost, or data is lost due to data overflow), the DCE returns an ‘ERROR’ message to the DTE; the DTE should then discard the frame.

Note: If the telephone line is on-hook, the modem responds back to the DTE with an ‘ERROR’ message whenever any of the fax AT commands, except the +FCLASS command, are sent to the modem.

Figure 9. CLASS 1 DTE-Generated HDLC Frame Information (AT+FTH=<mod>)

Address

Field

Control

Field

Facsimile

Control

Field

Facsimile

Information

Field

Figure 10. CLASS 1 DTE Reception of HDLC Frame Information (AT+FRH=<mod>)

Address

Field

Control

Field

Facsimile

Control

Field

Facsimile

Information

Field

Frame

Checking

Sequence

(FCS)

Like the data modem mode, the DTE needs to issue an ATD string or ATA command to the modem to originate or answer a fax call. Unlike the data modem mode, auto-answering is not supported by the modem while in fax mode. It is recommended that S-register S0 be set to ‘0’ (that is, use ‘ATA’) whenever the modem is expected to receive a fax call.

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536EX Chipset Developer’s Manual

Intel Confidential

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Intel 537EX manual Hdlc Frame Format, Class 1 DTE-Generated Hdlc Frame Information AT+FTH=mod
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537EX specifications

The Intel 537EX is a powerful and innovative embedded processor designed for a range of applications, particularly in the fields of industrial automation, telecommunications, and transport management systems. This processor is a member of Intel's embedded product line, tailored specifically to meet the demands of systems that require high reliability and long lifecycle support.

One of the main features of the Intel 537EX is its multi-core architecture, which enables efficient parallel processing capabilities. This allows for the execution of multiple tasks simultaneously, significantly improving overall system performance. The processor also incorporates Intel’s advanced power management technology, which ensures that the device consumes energy efficiently, enhances thermal performance, and prolongs the lifespan of the system.

The Intel 537EX supports a range of connectivity options, including high-speed Ethernet and Serial ATA interfaces. This ensures that it can easily integrate into existing systems, seamlessly supporting applications that require robust data transfer capabilities. Additionally, the processor is equipped with multiple I/O ports, facilitating the connection of various peripherals and sensors, which is crucial in industrial applications.

One of the standout technologies within the Intel 537EX is its support for hardware virtualization. This feature allows for the creation of multiple virtual environments within a single physical structure, optimizing resource utilization and enhancing system flexibility. Additionally, Intel’s integrated security technologies provide a significant layer of protection against potential threats, ensuring that embedded systems remain secure.

Another characteristic of the Intel 537EX is its extensive software support, which includes compatibility with various operating systems and development environments. This versatility makes it an attractive choice for developers looking to build or upgrade their embedded systems. With access to Intel's comprehensive software tools, developers can quickly optimize applications to take full advantage of the processor's capabilities.

The Intel 537EX also boasts excellent thermal performance, allowing it to operate efficiently in harsh environments. This is crucial for embedded applications in industrial settings where temperature fluctuations are common. Overall, the Intel 537EX is engineered to deliver high-performance processing power, superior connectivity, and enhanced security, solidifying its position as a reliable choice for demanding embedded applications.
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