Moog MSD Servo Drive Series User Manual

SSI encoder basics and requirements
The SSI interface on the MSD Servo Drive has been designed as an actual motor
feedback interface. Accordingly, the connected SSI encoder must meet the following
criteria:
 Clockanddatainactivelevel=HIGH
 Thecurrentpositionmustbeinternallystoredatthefirstfallingclockedge
 Nolengthenedcalculationtime(infirstcycle)
 Withthefirstrisingclockedge,theencodermustshiftthedatatothefirst
positionbittobetransmitted(MSB)
 1Mbpsrate
 Datacoding=BinaryorGray
 Readingdataafterthedatabitsendispermissible
 125µscycle(i.e.internalpositionrefreshrate≪125µs)
 Monofloptime≥6µs
 Datalinesdrivenwithlogic0duringmonofloptime
 Noparitybit
 Noerrorbitsorotherstatusbits
 ≤14MultiTurnbits
MOOG
ID
No.: CB40859-001 Date: 02/2018
MSD Servo Drive- Device Help
67
6 Encoder
SSI wire break monitoring (bit monitoring during monoflop time)
If monitoring is enabled, the drive, as the SSI clock master, will read data for one
more clock cycle after the data bits (reading data after the data bits end is
permissible). The bit that the master reads in addition to the data bits this way comes
from the SSI encoder’s monoflop time. At the time corresponding to this bit, the SSI
encoder must drive the data lines with a logic 0. If the data lines on connector X7 are
open, a logic 1 will be read here. The bit monitoring at this point makes it possible to
determine whether the SSI data lines are being actively driven with a logic 0 at this
point (no “wire break”) or are not (“wire break”). SSI wire break monitoring can be
disabled by setting P546[0] - ENC_CH1_Modeto0001h.
Mode parameters and CycleCount parameters
P546[0] - ENC_CH1_Mode can be used to run a parity evaluation after the data. In
addition, ENC_CH1_Mode makes it possible to run special SSI encoders that deliver
one or more special bits after the data. In this case, the MSD Servo Drive will not
evaluate these bits – this mode is meant to make it possible to work with SSI
encoders that require for these bits to be sampled. P616[0] - ENC_CH1_
CycleCount makes it possible to run slower SSI encoders that cannot handle the
required cycle of 125µs. The control characteristics will deteriorate when using this
type of SSI encoder, and for that reason it is not recommended.
ID Index Name Unit Description
505 0 ENC_CH1_Sel=2 =SSI(2)
543 0 ENC_CH1_MultiT NumberofMultiTurnbits(absoluteencoder)
544 0 ENC_CH1_SingleT NumberofSingleTurnbits(absoluteencoder)
545 0 ENC_CH1_Code Codeselection(SSIabsoluteencoder)
546 0 ENC_CH1_Mode Modeselection(SSIabsoluteencoder)
547 0 ENC_CH1_MTBase MinimumMultiTurnposition(SSIabsolute
encoder)
548 0 ENC_CH1_MTEnable Channel1:Multi-turnassingle-turn
598 0 ENC_CH1_Position inc Positionencoderchannel1
616 0 ENC_CH1_CycleCount Channel1:Positionencodersamplingcycle(nx
125µsec)
Table 6.12: Encoder configuration channel 1 (X7) - SSI parameters

Moog MSD Servo Drive Series Specifications

General

Brand	Moog
Model	MSD Servo Drive Series
Category	DC Drives
Language	English