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MSD Servo Drive User Manual SERCOS II
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[ Chapter 4 ]
4.3.1 Description of bits 13-15
Bit14: Drive ENABLE (power stage enable)
The MSD Servo Drive has a control input (X4.10) ENPO (Enable Power) for hardware en-
able. This input must be configured for operation of the power stage at 24 V.
The device additionally features the “STO” (Safe Torque Off) function, category 3 (see
MSD Servo Drive Operation Manual and Application Manual) via control input (X4.22)
ISDSH. The logic for this function (High edge at digital input ENPO (X4.10), with a High
signal required at the digital input ISDSH (X4.22) at the time the edge occurs) must be
fulfilled by the higher-level control system according to Application Manual.
NOTE: If the ENPO and ISDSH inputs are not configured, the device remains in
state 1 = “Not Ready to Switch On” or 2 = “Switch On Disabled”. In the STO
state the status indicator flashes “S1” or “S2” as appropriate.
Only after correct configuration of ENPO (X4.10) and ISDSH (X4.22) can the hardware
be enabled by bit 14 in the SERCOS control word MDT (Master Data Telegram). It is only
possible to enable the drive via bit 14 in communication phase 4.
Bit 15: Control ON/OFF (drive enable)
Control of the drive via the SERCOS interface requires just a few parameter settings:
• Open-loop control setting of drive via SERCOS interface: Set P-0-0159 to SERCOS
(6).
• Setpoints via SERCOS profile: Set P-0-0165 to SERCOS (8)
• Evaluation of bit 15 in MDT state-controlled (1 = LEVEL) or edge-controlled (0 =
EDGE) via P-0-0144.
Note:
If bit 14 and bit 15 in the MDT are set simultaneously, P-0-0144 must be set to
LEVEL (1).
In summary: For the drive enable signal (bit 15) to be accepted - that is, for the drive to
switch from the unpowered to the powered state - the following conditions must be
met:
• SERCOS interface ready and in communication phase 4
• Enable power pack via hardware (ENPO and ISDSH) and bit 14 in MDT
• Drive not in fault state
• Settings of relevant parameters P-0-0144, P-0-0159 and P-0-0165
Under these preconditions the drive shows device state “3” on the display. The drive is
activated by the change of state from 0 to 1 of bit 15 (drive enable) in the MDT. If the
enable is successfully executed, the display readout changes to 5 and the relevant bits in
the drive telegram (DT) are operated.
The readiness of the control (drive follows setpoints) is mapped in the status word via bit
15, bit 14 and bit 3.
Ideally, the master control system reads the actual value while control is starting and
presets it as the setpoint until the closed-loop drive signals readiness in the status word.
If the drive moves while control is starting (such as due to motor commutation finding by
linear drives, whereby the drive does not yet signal readiness - drive state 4), the position
changes are automatically adopted by the master control system.
Control systems which retrieve the current actual position “only once“ prior to start of
closed-loop control and preset it as the setpoint, and also do not update it even after
commutation finding (no evaluation of status word) will feed forward a setpoint differ-
ence. Shut-off due to tracking error may be the consequence.
To avoid this, the drive can be moved to the position specified by the master control
system at start of control under drive control with parameter P-0-0156 (Enable operation
option code) set to MOVE_COMMAND(1). This aims to exclude the possibility of a shut-
off or a jerky approach to the target position at start of control because of a setpoint
difference in the axis.
This function also depends on the configuration of P-0-0743 (maximum tracking error).
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