User's Manual

Turbo PMAC PCI HRM
Machine Connections 31
Motor Signals Connections (JMACH Connectors)
Resistor Pack Configuration: Termination Resistors
The PMAC PCI provides sockets for termination resistors on differential input pairs coming into the board.
As shipped, there are no resistor packs in these sockets. If these signals are brought long distances into the
PMAC PCI board and ringing at signal transitions is a problem, SIP resistor packs may be mounted in these
sockets to reduce or eliminate the ringing.
All termination resistor packs are the type that have independent resistors (no common connection) with
each resistor using two adjacent pins. The following table shows which packs are used to terminate each
input device:
Device Resistor
Pack
Pack Size Device Resistor
Pack
Pack Size
Encoder 1 RP61 6-pin Encoder 5 RP98 6-pin
Encoder 2 RP63 6-pin Encoder 6 RP100 6-pin
Encoder 3 RP67 6-pin Encoder 7 RP104 6-pin
Encoder 4 RP69 6-pin Encoder 8 RP106 6-pin
Resistor Pack Configuration: Differential or Single-Ended Encoder Selection
The differential input signal pairs to the PMAC PCI have user-configurable pull-up/pull-down resistor
networks to permit the acceptance of either single-ended or differential signals in one setting, or the
detection of lost differential signals in another setting.
The ‘+’ inputs of each differential pair each have a hard-wired 1 kΩ pull-up resistor to +5V. This cannot be
changed.
The ‘-‘ inputs of each differential pair each have a hard-wired 2.2 kΩ resistor to +5V; each also has another
2.2 kΩ resistor as part of a socketed resistor pack that can be configured as a pull-up resistor to +5V, or a
pull-down resistor to GND.
If this socketed resistor is configured as a pull-down resistor (the default configuration), the combination of
pull-up and pull-down resistors on this line acts as a voltage divider, holding the line at +2.5V in the absence
of an external signal. This configuration is required for single-ended inputs using the ‘+’ lines alone; it is
desirable for unconnected inputs to prevent the pick-up of spurious noise; it is permissible for differential
line-driver inputs.
If this socketed resistor is configured as a pull-up resistor (by reversing the SIP pack in the socket), the two
parallel 2.2 kΩ resistors act as a single 1.1 kΩ pull-up resistor, holding the line at +5V in the absence of an
external signal. This configuration is required if encoder-loss detection is desired; it is required if
complementary open-collector drivers are used; it is permissible for differential line-driver inputs even
without encoder loss detection.
If Pin 1 of the resistor pack (marked by a dot on the pack) matches Pin 1 of the socket (marked by a wide
white line on the front side of the board) and a square solder pin on the backside of the board, then the pack
is configured as a bank of pull-down resistors. If the pack is reversed in the socket, it is configured as a
bank of pull-up resistors.
The following table lists the pull-up/pull-down resistor pack for each input device:
Device Resistor
Pack
Pack Size Device Resistor
Pack
Pack Size
Encoder 1 RP60 6-pin Encoder 5 RP97 6-pin
Encoder 2 RP62 6-pin Encoder 6 RP99 6-pin
Encoder 3 RP66 6-pin Encoder 7 RP103 6-pin
Encoder 4 RP68 6-pin Encoder 8 RP105 6-pin