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ACC24E2S TTL output hardware problems


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I have had trouble with motor motion when no commanded moves are given and moves in only a single direction. I have the step, direction and AENA outputs connected to an IMS MForce amplifier with a grounded reference to drive the motors.


I strongly suspect the problem is with TTL levels being drawn down when attached to the amplifier. The step and direction levels drop from 5V to 3.4V when connected to the amplifier resulting in a not totally defined high or low state.


There are major problems with the AENA. First off, is it an input or output? You have it listed as both an input and I/O in the manual. I do not understand your design if is meant to be an input only. How are we intended to enable the amplifier otherwise?


There are similar discrepancies in the ACC24E2A manual about amplifier enable. Some places you have it listed as an input and some as an output (specifically for the AE_COM pin).

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The ACC-24E2S uses MC3487 differential line drivers for its outputs: PULSE+, PULSE-, DIR+, DIR-, AENA+, AENA-. These have 1-kohm pullup resistors and 33-ohm in-line current limiting resistors on each line. If these cannot hold a high voltage close to 5V when attached to your amplifier, your amplifier must be providing a very low resistance path to 0V (that is, a very strong pull-down, much stronger than the 1-kohm pullup). This would be very unusual, and probably indicates that something is wrong. The line drivers can easily supply 10mA without significant droop.


The AENA+/- output signals use the same pins that are normally used for the encoder index (C+/-) inputs. You must install the appropriate jumper for the channel (E11, E12, E13, E14) to be able to use these pins for the AENA+/- outputs.

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Hi Curt,


I have the jumpers E11-E14 already installed on the board. The AENA only seems to output 0.15V (Low) and 3V (high) when not connected to anything. When it is connected to the amplifier in sinking configuration, the levels are at 2.3 and 2.8V low and high respectively.


I have tried in both the sinking and sourcing configuration and neither are producing acceptable pulse levels for Pulse, Dir, and AENA simultaneously.


I have attached the specifications of the amplifiers I am using.


I will also contact the amplifier manufacturer to find out why it may be pulling the levels down.





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