PPMC Encoder Board

Features :

The Parallel Port Motion Control Encoder board has 4 24-bit quadrature encoder counters. The board provides up to 200 mA at 5V to each of the 4 encoders through resettable (PTC) fuses.

There are two versions of the encoder board available, one supports only single-ended encoder inputs, the other will support both single-ended and differential encoders in any combination. The choice between single-ended and differential inputs is made through jumpers, on a channel by channel basis.

The Encoder is capable of generating a servo cycle clock that can be selected under software control from 625 Hz to 10 KHz in 16 steps (10 KHz divided by a factor of 1 to 16). This clock can be provided to additional encoder boards and DAC16 boards, so all encoders and DACs sample and update synchronously.

The encoder board occupies a block of 16 consecutive addresses on the EPP (IEEE 1284 protocol) bus. The high 4 address bits are specified through a 4-position DIP switch marked SW1. The Most significant bit (bit # 7) is switch 4, the least significant fixed address bit (bit # 4) is switch 1.

Connectors :

P2 through P5 connect to the encoders. P2 is for channel 0, the first Axis. P5 is for channel 3, the last Axis. With the component side of the board UP, and these connectors facing you, pin 1 is on the Left. Pins are as follows :
Pin # Signal
1 +5 V
2 Ground
3 A
4 B
5 Z
6 A/ Differential Only
7 B/ Differential Only
8 Z/ Differential Only
A and B are the quadrature signals from the encoder. If you have an encoder with an index channel, this is connected to the Z input. For differential encoders, the A/ B/ and Z/ inputs are used for the complemented signals.
JP13 is factory set for normal operation. It can be broken to allow downloading the FPGA program from a computer during debugging. With the jumper in the factory (closed) state, the FPGA downloads its program from the SPROM in U2. A failure of the FPGA program to correctly load is indicated by a steadily lit LOAD FAIL LED. If the program does not load correctly (this should not happen in the field) it could be due to slow or erratic rising of the +5 V power supply.
On boards which have the differential input option, the following jumper positions are used to select input mode for individual channels. Single-ended is selected with the jumpers to the left (as the board is shown in the drawing below), and differential is selected with the jumper to the right.
Channel # Jumpers
0 JP1, 2 & 3
1 JP4, 5 & 6
2 JP7, 8 & 9
3 JP10, 11 & 12
Board Layout

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