6.1.12.3 Go To Local;
A simple command message that places the amplifier into
the local mode, allowing control via the ‘user interface’ discrete control lines. Data
requests via the serial communications interface will continue to be serviced in the
local mode, however commands other than ‘Remote enable’ will be rejected as non-
executable (see section 6.4.1 for details of message format).
6.1.12.4 Remote Enable;
A simple command message that places the amplifier
into the remote mode, allowing control via the serial communications interface.
When in the remote mode, the standby and transmit ‘user interface’ discrete control
inputs are disabled; all other control inputs and monitor outputs remain active.
6.2
Protocol
6.2.1
Interface and Termination
RS-485 compatible 4-wire with no receiver biasing option. When using this amplifier
with the serial communications interface, a 120
O
bus termination should be fitted
externally between the Rx+ (pin d) and Rx
7
(pin e) connections of the 41-pin
control connector. If used in the redundant mode with another amplifier, or on a
multi-drop system, the bus termination is only required on one equipment, typically
the furthest from the master device.
A screened cable, terminated to the backshell of the user interface connector, should
be used to prevent radio frequency interference from adversely affecting operation;
when connecting the screen of the cable to the backshell, a full 360
8
electrical
connection should be made (pig-tailed connections should be avoided).
For short cable runs up to approximately 5 m, a suitable data transmission cable
would include a twin twisted pair conductor arrangement, typical conductor size of
24 to 26 AWG, screened in aluminised tape with an overall tinned copper braid. A pin
is provided on the connector for the connection of a drain wire if available on the
cable. For cable runs above 5 m, an additional insulated conductor core should be
used as a signal return connection.
6.2.2
Data format
The format is:
1 start bit
8 data bits with most significant bit sent as EVEN parity
1 stop bit
Which can be realised as:
1 start bit
7 data bits
EVEN parity
1 stop bit
6.2.3
Data Rate
The default data rate is 9600 baud but other baud rates may be selected using the
appropriate command.
HBN63xx-1, Issue 8, Page 32
