Tait T2000-A75, Руководство по эксплуатации

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8 M2256-000-00-051 November 2001
Command mode
In Command mode, the PC sends command sequences to the A75 and waits for a prompt before
beginning the next transaction. The A75 sends a prompt character ‘.’ to the PC to indicate that
it is ready to accept a new command. Some commands require the A75 to send a CCDI message
in response, before it sends the prompt.
Messages directed to the A75 will always be responded to, either by a return message, or by the
presence of the prompt.
Messages from the A75 are either solicited or unsolicited. Solicited messages are sent in re-
sponse to commands from the PC. Unsolicited messages such as
PROGRESS or ERROR mes-
sages are sent by the A75 if there is a significant change in the state of the T201X that the PC
should be aware of. When errors are detected, an unsolicited
ERROR message is sent by the
A75 to the PC. The A75 does not send messages that require a reply.
Transparent mode
Transparent mode creates a direct link between the PC and the FFSK modem located on the
A75. The transparent link allows the PC to send and receive data without having to pass mes-
sages using the CCDI Command mode.
The transparent link is administered by the A75 which reads FFSK data arriving from another
FFSK modem and sends it to the serial port. Any form of binary data is acceptable but the escape
sequence to switch back to Command mode should be avoided. The escape sequence character
is set to ‘+’ by default, or defined within the TRANSPARENT command.
PROGRESS messages are unsolicited status messages sent by the A75 but can be filtered out
in Transparent mode by enabling TMODE Filter control with the FUNCTION command. When
the TMODE filter is enabled, progress messages are not sent by the A75. When a PROGRESS
message is sent in Transparent mode, the escape character is attached to the front of the mes-
sage, e.g. zzzp0207C7 where ‘z’ is the escape character.
In Transparent mode, the A75 does not generate or detect CRC checksum data. However if a
SDM message is transmitted or received then the CRC checksum data is used.
Transparent mode serial baud can be set to either 9600, 4800, 2400 or 1200 baud using the PRO-
GRAM command.