Microsoft LPF-00004 Manuel de l'opérateur télécharger pdf (Page 112)

Page 94 PROGRAMMER'S GUIDE

YBER

380, COPYRIGHT MARCH 2002, AXON INSTRUMENTS, INC.

PROGRAMMER'S GUIDE

This chapter provides information for programmers who wish to add CyberAmp control to any

program.

This guide assumes that the programmer is familiar with the features and basic operation of the

CyberAmp380, as described in the Introduction and Functional Description chapters.

Serial-Port Communcations

Communications with the CyberAmp 380 are via the RS-232 serial port. All commands and

responses are in plain ASCII. Certain conventions adhered to by the CyberAmp 380 and other Axon

products are described in this section.

1) Axon Expandable RS-232 Bus

The RS-232 bus used by the CyberAmp 380 is slightly non-standard. The transmit lines have

been protected by diodes so that multiple instruments can be connected without damage to the

same serial port. Up to ten devices can be connected to a single serial port. A rate of 19,200 baud

can be sustained if the total daisy-chained cable length is less than 6 m (20 ft). Longer cable

lengths are possible if the baud rate is reduced.

Each instrument has an address switch on the back panel, labeled from 0 to 9. All instruments

continually listen for commands from the host. An instrument will only respond if the command

specifies the instrument's address.

This is not a general-purpose bus. It relies on the principle that an instrument will not speak

unless spoken to by the host. Only one host is permitted on the Axon Expandable RS-232 bus.

All instruments on the Axon expandable RS-232 bus must use the "AT" command protocol

described below.

2) Auto Baud Rate

The CyberAmp 380 determines the correct baud rate automatically. Baud rates from 300 to

19,200 are supported. To enable the CyberAmp 380 to determine the baud rate, each command

string from the host computer must commence with the letters "AT". The CyberAmp 380

calculates the baud rate from the first bit in the letter "A". It calculates the parity from the

letter "T".

3) Parity

Parity can be even, odd, high or low.

4) Stop Bits

One or more stop bits are acceptable.

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Microsoft LPF-00004 Manuel de l'opérateur Page 112