7
Switches S1 and S2: Clock Source
The setting for Switches S1 and S2 determines the source of the
HSSI Terminal Timing (TT) for the 2042MC-MT. With Switch S1 On
and S2 Off, the Model 2042MC-MT derives the HSSI Terminal Timing
from the ST signal provided by the HSSI DCE. With Switch S1 Off,
and S2 On, the RS-530 DTE provides TT to the HSSI DCE.
S1
S2
Description
Off
Off
Not a Valid Setting
Off
On
Terminal Timing Supplied by RS-530 DTE
device
On
Off
Terminal Timing supplied by HSSI ST signal
On
On
Not a Valid Setting
Switches S3 and S4: Synchronization Method
Switches S3 and S4 allow the Model 2042MC-MT to compensate
for timing delays when transmitting HSSI data at high speeds (greater
than 2.5 Mbps). At high bit rates, set Switch S3 On and Switch S4 Off.
In this setting, the RS-530 data will be synchronized to the SD timing
signal before conversion to HSSI. At lower bit rates (less than 2.5
Mbps), set Switch S3 Off and S4 On. In this setting, the RS-530 data
bypasses the synchronization circuit and is passed straight through to
the HSSI DCE.
S3
S-4
Description
Off
Off
Not a Valid Setting
Off
On
Data Skips Sync Circuit
On
Off
Data passes through sync circuit.
On
On
Not a Valid Setting
2042MC-MT DIP SWITCH SUMMARY TABLE
Position
Function
Factory Default
S1
Clock Source
On
S2
Clock Source
Off
S3
Sync Method
Off
S4
Sync Method
On
}
}
HSSI ST
Signal
Bypass
Sync Circuit
8
3.2 CONFIGURATION SWITCHES (MODEL 2042MT-MC)
The Model 2042MT-MC has miniature DIP switches that you may
use to configure the units. Each Model 2042MT-MC is factory config-
ured as DTE on the RS-530 end, and DCE on the HSSI end.
Therefore, the RS-530 end “wants” to plug directly into a DCE device.
Conversely, the HSSI end of the converter “wants” to plug directly into
DTE.
Please use this section to configure the internal DIP switches so
that the unit will work properly in your application. Figure 5 shows the
position of the DIP switches on the top side of the PC board.
Figure 6 shows the orientation of the Switches on DIP Switches S1
through S4 with respect to ON/OFF positions. The default settings for
DIP switch S1 are shown in the table on page . Detailed descriptions
of each switch follow the table.
Figure 5. The Model 2042MT-MC Assembly Drawing
1234
Figure 6. Close-up of DIP Switches Showing “ON” and “OFF” Positions
1
2
3
4
ON
OFF
ON
DIP Switches S1 - S4
ON
OFF
