Microsoft LPF-00004 Manual del operador descargar pdf (Pagina 113)

PROGRAMMER'S GUIDE Page 95

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380, COPYRIGHT MARCH 2002, AXON INSTRUMENTS, INC.

"AT" Command Protocols

The "AT" command set consists of ASCII commands and rules governing the commands that are sent

by the host computer to instruments on the Axon expandable RS-232 bus.

1) Each command from the host must commence with the letters "AT". Upper case is required for

the letters "AT" but case is irrelevant for subsequent characters in the command string. This

prefix is crucially important because it is used by the instrument to determine the baud rate and

the parity.

An incidental benefit of prefixing all command strings with "AT" is that it ensures that the

instrument will not respond to spurious characters on the serial port.

2) The third character in the command string is usually a number from 0 to 9. This is the address of

the device for which the command is intended. This manual uses "d" for "device" number when

referring to this address.

If no device number is specified, all devices on the bus will respond. (There is a potential

conflict if more than one device is connected.) This mode of operation is useful for test and

development purposes. However, application programs should always specify a device number.

3) All characters after the "ATd" prefix represent the command.

4) Certain commands are reserved as being applicable to all instruments that reside on the Axon

expandable RS-232 bus. At the time this manual was printed, only one such command was

defined. This is "ATdS", where "S" stands for status.

On receipt of an "ATdS" command, the instrument numbered "d" must respond with a

description of its model number and ROM version number. By sequentially issuing the ATdS

command for all values of d from 0 to 9, the host computer can determine what instruments are

connected to the bus.

There is a verbose form of this command, called "ATdS+". The instrument numbered "d" must

respond with a description of its model number, serial number, ROM version number and the

internal settings, in a prescribed format.

5) All command strings from the host must be terminated by a carriage return. All responses from

the instrument are terminated by a right arrow, ">".

6) If a command is not recognized, or if there is an error executing the command, the instrument

responds with a question mark (?) followed by a carriage return and the right arrow.

7) Multiple commands can be concatenated into a single command string, prefixed by "ATd" and

terminated by a carriage return. Spaces can be inserted between commands to improve clarity.

Spaces can also be inserted between commands and data. There is a 64 character limit to the

command string length.

8) Leading zeros are always ignored and do not have to be supplied.

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Microsoft LPF-00004 Manual del operador Pagina 113