Scanivalve MPS4264, Руководство по аппаратному и программному обеспечению, Страница: 29 / 99

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MPS4264
Section 3: Operation
returned. Review the list to ensure it in inclusive of all units
that are expected to be included in the cluster. Once this
has been verified, a scan on all units can be initiated with
the command:
MSCAN
If at any point the scan needs to be terminated, issue the
command:
MSTOP
There are three “multiple unit” commands that allow
control of the cluster of scanners. They are:
Multiple Unit Scan Command
Multiple MPS units are started scanning by connecting
to one MPS and issuing a MSCAN command. This device
becomes the master and reissues a multicast SCAN
command. See the table below for the scan start packet
format. All devices that are set up to listen to this multicast
address will respond to the SCAN command. The slave
devices must still fulfill the SSD and SST requirements for
starting a scan.
Table 3-1: MSCAN Packet Format
FUNCTION BYTES
DATA
TYPE
DESCRIPTION
Packet Type 2 Integer 0202
Further information on the MSCAN command can be found
in “Multiple Unit Scan” on page 50.
Multiple Unit Stop Command
Multiple MPS units are stopped scanning by connecting
to one MPS and issuing a MSTOP command. This device
becomes the master and reissues a multicast STOP
command. See the table below for the stop packet format.
All devices that are set up to listen to this multicast address
will respond to the STOP command.
Table 3-2: MSTOP Packet Format
FUNCTION BYTES
DATA
TYPE
DESCRIPTION
Packet Type 2 Integer 0303
Further information on the MSTOP command can be found
in “Multiple Unit Stop” on page 42.
Multiple Unit Find Command
The user may connect to one MPS4000 and issuing a
MFIND command. This command will return a list of all
devices that are part of the multicast cluster. The MFIND
command used the Discovery Packet described below.
Table 3-3: MFIND Packet Format
FUNCTION BYTES
DATA
TYPE
DESCRIPTION
Packet Type 2 Integer 0101
Further information on the MFIND command can be found
in “Multiple Unit Find” on page 42.
Scanning with an External Trigger
The MPS4264 can be configured to scan with an external
hardware or software trigger. This provides a simple means
of synchronizing the data collection between multiple MPS
scanners when an IEEE-1588 architecture is not in place. It
also provides a means of synchronizing MPS scanners with
other equipment that may not be IEEE-1588 compatible.
The MPS4264 has several options for external triggering.
The external trigger can be use in one of three ways:
1. Hardware Frame Trigger
2. Hardware Scan Trigger
3. Software Frame Trigger
Options 1 & 3, the “frame trigger” options allow an
external trigger (either hardware or software) to release
a single frame of data. This means for a single trigger
pulse (or command) the MPS will return a single frame of
averaged data. Option 2, the “ Hardware Scan Trigger”
option means that a if the trigger input level is “high”
(5Vdc<voltage<15Vdc) the MPS will enter scan mode where
it will scan and continuously collect data based on its
internal clock. The MPS will continue to scan at this rate
until any of the following conditions are met:
• The trigger input level is switched to “low” (<5Vdc)
• FPS term is met
• The scan is manually stopped with the STOP
command
The external hardware trigger voltage is input through
pins 4 & 5 of the power connector. The trigger is 5-15Vdc,
6.5mA. A wiring diagram for the power/serial/trigger cable
can be found in “Serial Communications” on page 14.
The external software trigger is a command sent to the
MPS. The trigger can be one of two commands, either a
TRIG command or a <tab>. More information on the TRIG
variable can be found in “Set Trigger (TRIG)” on page 55.
Information on the software trigger can be found in “Soft-
ware Frame Trigger” on page 50.
Setting up an External Frame Trigger
To configure the MPS4264 to scan with an external frame
trigger:
1. Set the variable “TRIG” to 1
2. Set the “RATE” variable to a rate that is approxi-
mately 25% faster than the intended trigger rate
3. Set the MPS into “scan” mode by sending the
command: SCAN
4. Supply a trigger, either hardware trigger pulse or a