User's Manual

PMAC User Manual
Input/Output: Connecting PMAC to the Machine 47
Direction Bit Use
An alternate use for these outputs is as the direction (sign) bits for drive systems expecting sign-and-
magnitude commands. Some servo amplifiers expect this command format, and if the signal needs to be
run through a voltage-to-frequency converter such as the Acc-8D Opt 2 to create a pulse train for a
stepper drive, this format should be used. To use the output in this manner, bit 16 of Ix25 for the motor
using this line must be set to 1. This disables its use as an amplifier-enable line. In addition, bit 16 of
Ix02 for the motor must be set to 1. This makes the analog output an absolute value, and places the sign
bit on this output.
General-Purpose Use
If no dedicated use is made of this output, it may be used as a general-purpose output by assigning an M-
variable to the bit (M114, M214, etc., in the suggested M-variable definitions).
Compare-Equals Outputs
The compare-equals (EQU) outputs have a dedicated use of providing a signal edge when an encoder
position reaches a pre-loaded value. This is very useful for scanning and measurement applications.
Instructions for use of these outputs are covered in detail in the Synchronizing PMAC to External Events
section of this manual.
PMAC PC
On the PMAC PC, there is not a framed connector for the EQU outputs. However, these signals may be
brought out by placing a 26-pin IDC connector over the 13 E-point pairs E53 to E65, which include the
eight EQU lines. These outputs are TTL-level with very low drive capability; they must be buffered
externally before they can drive any real devices. Acc-27, normally used as an I/O buffer for the
thumbwheel multiplexer port, can be used to drive several of these EQU lines. The 26-pin cable provided
with the Acc-27 fits over the 13 jumper pairs E53-E65.
PMAC VME
On PMAC VME, these signals are brought out on connector J7 (JEQU), referenced to digital ground
(GND). As shipped from the factory, they are open-collector (sinking) outputs, with a ULN2803A driver
IC, rated to 24V and 100mA each. They may be changed to open-emitter (sourcing) drivers by replacing
this chip in U28 with a UDN2981A driver IC and changing jumpers E93 and E94.
PMAC Lite
On PMAC Lite, these signals are brought out on connector J8 (JEQU), optically isolated from the digital
circuitry, referenced either to analog ground (AGND) or an external flag supply ground. As shipped from
the factory, they are open-collector (sinking) outputs, with a ULN2803A driver IC, rated to 24V and
100mA each. They may be changed to open-emitter (sourcing) drivers by replacing this chip in U54 with
a UDN2981A driver IC and changing jumpers E101 and E102.
PMAC STD
On PMAC STD, these signals are brought out on connector J6 (JEQU) on each of the piggyback boards.
They are open-collector (sinking) outputs with internal 1 kΩ pull-up resistors, rated to 5V.
On PMAC STD1.5, these signals are brought out on connector J8 (JEQU), optically isolated from the
digital circuitry, referenced either to analog ground (AGND) or an external flag supply ground. As
shipped from the factory, they are open-collector (sinking) outputs, with a ULN2803A driver IC, rated to
24V and 100mA each. They may be changed to open-emitter (sourcing) drivers by replacing this chip in
U54 with a UDN2981A driver IC and changing jumpers E101 and E102.