Western Telematic CAS-81 manual Command Response, Open Port Gating, Close Port Gating

CAS-81 Code Activated Switch, User's Guide Operation

4.4. Command Response

Upon receiving a valid command string, the CAS-81 will send an acknowledgment message out the Control Port. The message is sent as 8 bits / no parity. Acknowledgment messages are as follows:

Connected <CR>/<LF>

Disconnected <CR>/<LF>

Broadcast <CR>/<LF>

Note that the Command Response can be disabled by placing DIP Switch 6 in the UP position to enable the Quiet Mode feature. When the Quiet Mode is active, the unit will not send acknowledgment messages.

4.5. Port Gating

With all ports closed, data received by the Control Port will not be passed to any of the Serial Ports. Any data received by the Serial Ports will not be passed to the Control Port. The CTS and DCD signals will always be set high.

4.5.1.Open Port Gating

Upon receiving a valid command string at data rates up to 19,200 bps, the selected Serial Port will open during the stop bit time of the configuration code thus allowing the next character to be passed out the selected port.

For data rates above 19,200 bps it is necessary to delay approximately 1 millisecond before sending data out the selected Serial Port. This prevents a character that immediately follows the configuration character from being "cut in half".

4.5.2.Close Port Gating

Selected Serial Ports can be closed using three methods:

1.By using the Command String to select another Serial Port.

2.By Using the Command String to disconnect.

3.By using the No-Data-Activity timeout feature.

In methods 1 and 2, the Command String Control Codes will be passed out the selected Serial Port. The Serial Port(s) will close immediately after the sixth character, thus blocking the next character from being sent. If the configuration character was 1 - 8, then the selected Serial Port would open. If the configuration character was 0 then the ports would remain closed.

The No-Data-Activity timeout feature can be used to make a "clean" close if the Command String Control Codes cause a conflict with the connected devices. The Serial Port will automatically close if no data is received from the Control Port for the time period selected by the setup switch.

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