MDS 05-2415A01, Rev. A PROGRAMMING AND DIAGNOSTICS 3-3
Special Instructions for Radios Configured as TTL
In most cases, an HHT can be plugged directly into the radio’s
INTERFACE connector and used immediately. However, in some cases,
the INTERFACE connector may have been configured for TTL operation
(as opposed to the more common RS-232 format) using the radio’s J11
jumper.
If you are unsure of which configuration you have, look at J11 on the
transceiver’s motherboard. In an RS-232 radio, J11 pins 1-2 will be empty
(open).
If your radio is configured for TTL, an optional TTL to RS-232 adapter plug
is available from MDS (P/N 03-2223A01) to allow connection of the HHT
or other RS-232 equipment, making the transceiver appear as an RS-232
device. Contact MDS for ordering information.
If the TTL to RS-232 adapter plug is not available, it is also possible to
temporarily reconfigure the INTERFACE connector for RS-232 operation
by removing the jumper on J11 pins 1–2. (See Table 2-4 for proper jumper
placement.) When testing is complete, J11 can be restored to its TTL
configuration.
NOTE
Plugging an HHT or a PC into a transceiver configured for TTL signaling
will key the radio transmitter, and will not allow terminal operation.
However, no damage will be done to the terminal or radio.
Opening The Diagnostic Channel
The diagnostic channel between the HHT and the transceiver is automatically opened when a
HHT is connected to the transceiver. However, if an older HHT or transceiver is being used,
it must be opened before HHT functions can be performed. To manually open the diagnostic
channel when using older HHTs or transceivers, follow the steps below:
1. After the HHT has completed its self-check, look for a solid flashing cursor on its
display. This indicates that the Diagnostic Channel is closed and that the HHT is
ready to accept the
OPEN command.
2. Press ENTER . Wait at least five seconds to satisfy the required “quiet time.”
3. After the five second quiet time, type
OPEN + ENTER .
4. When the channel opens, the message "
DIAGNOSTICS IS OPEN" appears.
NOTE
If the Diagnostics Channel does not open the first time, wait at
least 5 seconds before trying again.
When the Diagnostics Channel is open, any keyboard entry is echoed by the transceiver and
appears on the HHT display. In radios that have a modem installed, the received data (RD)
and the transmit data (TD) LEDs will flash to indicate the exchange of information between
the HHT and the radio’s microcontroller.
The radio’s microcontroller and the modem share the communications lines connected to the
INTERFACE connector. In this way, no data will be passed through the modem to the
transmitted signal when the INTERFACE connector is connected to the HHT and the
diagnostics channel is open.
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