Chapter 6. Serial I/O, SNP & RTU ProtocolsGFK-2222AD April 2018 2196.2.12 Autodial Function (4400)This feature allows the CPU to automatically dial a modem and send a specified byte string.To implement this feature, the port must be configured for Serial I/O. After the autodial function isexecuted and the modem has established a connection, other serial I/O functions (Write bytes, Set UpInput Buffer, Flush Input buffer, Read port status, Write port control, Read bytes, Read String, and CancelOperation) can be used.ExamplePager enunciation can be implemented by three commands, requiring three COMMREQ commandblocks:Autodial:04400 (1130h)Dials the modem.Write Bytes:04401 (1131h)Specifies an ASCII string, from 1 to 250 bytes in length, to send from the serial port.Autodial:04400 (1130h)It is the responsibility of the application program to hang up the phone connection.This is accomplished by reissuing the autodial command and sending the hang upcommand string.Autodial Command BlockThe Autodial command automatically transmits an Escape sequence that follows the Hayes convention.If you are using a modem that does not support the Hayes convention, you may be able to use the WriteBytes command to dial the modem.Examples of commonly used command strings for Hayes-compatible modems are listed below:Command String Length FunctionATDP15035559999 16 (10h) Pulse dial the number 1-503-555-9999ATDT15035559999 16 (10h) Tone dial the number 1-503-555-9999ATDT9,15035559999 18 (12h) Tone dial using outside line with pauseATH0 5 (05h) Hang up the phoneATZ 4 (04h) Restore modem configuration to internally saved values
