User Manual M3000® Automation System / MSC II (Moog Servo ...

10 MSC II (Moog Servo Controller) Digital Sensor Interfaces
A
B
Z
t pl
t pl
t ph
t ph
Reversal Point
t d
Figure 65: Timing requirements of incremental encoder signals
Time Minimum Description
tpl 125 ns Minimum pulse high time
tph 125 ns Minimum pulse low time
td 1 ns Edge to edge minimum delay time
The incremental encoder provides relative position information. The position
value is incremented or decremented depending on the lead/lag relationship
of the two signals (A and B) delivered by the incremental encoder. These signals
may vary in frequency. The implemented interface can react on frequencies
up to 8 MHz.
The position data is counted in a 32 bit free running counter. Each A/B signal
edge triggers a 32 bit counter. This counter is overflowing to 0x0000 0000 or
underflowing to 0xFFFF FFFF, depending on direction.
Each pulse on the Z input may reset the counter to zero. This function must
be enabled by a MACS function block. By default the counter is free running
and Z input is ignored.
On the left side of the dotted line B signal is leading. On the right side of the
dotted line, the direction of the incremental encoder has changed. Now A is
leading.
Following relations between counter update and lead/lag of signals is implemented:
• while line A leads, the counter is incremented with every rising and falling
edge of line A and line B
• while line B leads, the counter is decremented with every rising and falling
edge of line A and line B
• if Z input is enabled, the counter is always reset to zero when a pulse occurs
on Z input
A
B
Counter: 5
Table 22: Timing of incremental encoders
Reversal Point
3 2 1 0 -1 -2 -1 0 1 2 4 8 16 20 24 28 32 36 40
Figure 66: Timing of Standard Incremental Encoder
10.13.4.2 Incremental Encoder (Pulse Train positive logic)
• On the left side of the dotted line, while B signal is low, the counter becomes
decremented.
• On the right side, while B signal is high, the direction has changed. Now
the counter becomes incremented.
Please make sure that any changes at B signal happen at least 100 ns
before a rising edge at A signal.
Timing requirements of
incremental encoder
signals
Timing of Standard
Incremental Encoder
© Moog GmbH User Manual M3000 ® and MSC II (CA65865-001; Version 1.1, 08/08) 106
t ph