Danaher Motion
06/2005
Project
M-SS-005-03 Rev
E
77
The first telegram in a communication cycle is the
M
aster
S
ynchronization
T
elegram (MST). The MST, issued by the controller. It provides a single
mark in time for all the drives. All feedback and command data are
synchronized for all axes via the MST.
Immediately after the MST is issued, each drive returns feedback and status
data in the
A
mplifier
T
elegram (AT). This includes position and velocity
feedback as well as responses to non-cyclic commands.
The final telegram in the communication cycle is the
M
aster
D
ata
T
elegram
(MDT). The controller issues the MDT. It contains information transmitted
from the MC, such as signals and position and velocity commands. The
service channel sends signals as well as non-cyclic commands.
3.12.3. Telegram
Types
SERCOS provides for a variety of telegram types. Different telegram types
define different sets of data to be exchanged in the AT and MDT. There are
seven standard telegrams in SERCOS. The simplest telegram is Type 0,
which defines only the service channel. No data are transferred in the cyclic
data. The most complex type is Telegram Type 7, which allows the user to
configure which data are in the cyclic data (all telegrams equally support the
service channel.) The other telegrams (Types 1 through 6) define different
combinations of position, velocity and current in the AT and MDT. The uses
only Telegram Types 5 and 7 for data communication.
Normally, the relies on the SERCOS
telegram type 5
. In Telegram
Type 5, position and velocity feedback are transmitted by the drive in
the AT cyclic data, and position and velocity command are transmitted
by the MC in the MDT cyclic data. These four components are the only
motion data transmitted in the cyclic data. Telegram type 5 works well
unless you need to have the external encoder position brought in with
the cyclic data. This is necessary when you want to slave an axis to the
external encoder In this case, you need to configure a Type 7 telegram.
When you need to bring an external encoder position from a drive to the
MC in realtime (cyclic data) you must configure a
telegram type 7
for
the drive. This telegram must contain all the motion data found in
telegram type 5 (position and velocity in both the AT and MDT), with the
external encoder position added.
To set up an axis for telegram type 7, you must modify the
SERCOSSETUP subroutine, which is generated as part of the BASIC
Moves auto setup program. You need to take the following steps:
Set
SERCOS.PHASE
to 0 and set the baud rate
Set the axis
PEXTFAC
of the axis with external encoder
Set the drive addresses (
DRIVEADDRESS
)
Set the axis
MASTERSOURCE
,
GEARRATIO
, and slave
properties of the slave axis
Set Sercos.Phase to 2
Configure the axis for Telegram Type 7 using IDN 15
Configure the AT for
VFB
,
PFB
, and
PEXT
(IDNs 40, 51, 53)
Configure the MDT for
VCMD
,
PCMD
(IDNs 36, 47)
Set
SERCOS.PHASE
to 4
See SERCOS Setup Subroutine in Appendix A for a sample subroutine.
