Motorola 900 series - HD-26 Connectors; HD26 Connector Pinouts

HD-26 Connectors
HD-26 Connectors
This section gives the pinouts of the HD-26 connectors used on the
MVME333P, MVME334AP, and MVME705-100 Series modules. These
connectors are configured for various serial interface standards by using Serial
Interface
Modules (SIMs). SIMs are small plug-in printed circuit boards
containing all the circuitry needed to convert a TTL-level synchronous or
asynchronous port to standard voltage levels needed by various industry
standard serial interfaces, such as EIA-232, EIA- 530, V.36. Separate SIMs exist
for DTE and DCE interfaces.
HD26 Connector Pinouts
All Serial Interface Modules share the following electrical characteristics:
1. All port signals (those going to the external connector) contain surge
suppression circuitry on the SIM. For EIA-232level signals, this is a 100
ohm series resistor and a dual15 volt clamp diode to chassis ground. For
EIA-422level drivers, each line contains a series 10 ohm resistor and a dual
15 volt clamp diode to chassis ground. For EIA-422level receivers,
EIA-423level drivers, and EIA-423 level receivers, each line contains a
series
100 ohm resistor and a dual 15 volt clamp diode to chassis ground.
EIA-422 level receivers used for clocks and data have a 100 ohm
termination resistor on the line side of the series resistors. All other
EIA-422level receivers are unterminated.
2. The Signal Ground pin on the connector is connected to local signal
ground via a 39 ohm resistor to limit current due to ground potential
differences. No connection is made between chassis ground and signal
ground at each serial port. This is a chassis-level function which must be
done elsewhere, usually on the VMEbus backplane.
S900RF/D4 B-9
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