Measurement Computing CIO-QUAD0x - Manual (Page 5)

1 INTRODUCTION
The CIO-QUAD02 is an ISA plug-in board that provides inputs and decoding for one or two incremental quadrature
encoders. A four channel version, the CIO-QUAD04, provides inputs and decoding for up to four encoders. Either the
CIO-QUAD02 or 04 can also be used as a high speed pulse counter for general counting applications.
PLEASE NOTE: If you have a CIO-QUAD04, all instructions in this manual apply. If you have a CIO-QUAD02, you
should ignore all references to channels 3 and 4. In all other respects, the two models are identical. In this manual, we will
refer to both boards generically as CIO-QUAD.
1.1 QUADRATURE ENCODERS AND THE CIO-QUAD
Incremental quadrature encoders are used to provide feedback signals from motors, that is, to count rotations and convert
the physical movement into a series of electrical signals. These signals are sent to the computer which then decides whether
or not to trigger signals that control the motor’s movement and what those control signals should be. The Measurement
Computing Corp. CIO-QUAD is the link between incremental quadrature encoders and the computer.
The CIO-QUAD is a plug-in board for PC/XT/AT computers; it uses one ISA slot and one rear panel opening for up to 2
channels (CIO-QUAD02) or one ISA slot and two rear panel openings for up to four channels (CIO-QUAD04). Each
incremental quadrature encoder connects to an input channel on the CIO-QUAD through a DB9 female connector on the
board’s rear panel. Channels 1 and 2 connect to the DB9 connectors attached directly to the board. Channels 3 and 4
(CIO-QUAD04) connect to the DB9 connectors on an auxiliary rear panel bracket.
For each channel, the signals at the DB9 connectors are:
O
Phase A+, A-
O
Phase B+, B-
O
Index +/-
O
+5 and GND (optional power for +5V encoders)
For pinout diagrams refer to Section 2.3.
The CIO-QUAD board provides inputs for three basic signals, Phase A, Phase B, and Index. Phase A and Phase B are
generated at a 90° phase shift with respect to each other. Using these signals, a computer with a CIO-QUAD can determine
system position (counts), velocity, (counts per second), and direction of rotation.
The Index signal is used to establish an absolute reference position within one count of the encoder rotation (360°).
Therefore, the Index signal is often used to reset or preset the position counter, particularly upon system startup when the
incremental encoder cannot determine the starting position of the motor. The Index signal can also be used to generate an
interrupt signal to the computer.
The Phase A, Phase B, and Index inputs are jumper-selectable for differential or single-ended input. These signals, after
being routed through differential receivers, offer various paths to the LS7266 inputs through the FPGA. The inputs are
register-selectable for:
O
individual incremental encoder inputs to allow up to four channels
O
cascadable counters to allow non-quadrature counting up to 96-bits
O
routing the Index input to either the Load Counter/Load Latch input or the Reset Counter/Gate input with quarter cycle
and half cycle signals supported
O
routing the Compare or Carry/Borrow output signals to the 8259 Interrupt controller
The heart of the CIO-QUAD is the LSI Computer Systems, Inc., LS7266R1 24-bit Dual Axis Quadrature Counter chip.
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