Versions Compared


  • This line was added.
  • This line was removed.
  • Formatting was changed.

Table of Contents

Theory Of Operation

Single RF Network Multipoint mode allows you have up to 8 WESs and 2 or more VSCs on single coordinated RF network while still maintaining Cat 3 PLd safety. Each VSC will monitor 1 or more WESs. You must configure 2 or more VSCs to monitor each WES to maintain the Performance Level and dual path redundancy required for Cat 3.

There is one RF master / Primary Coordinator VSC in the network. It polls the 8 possible WESs sequentially for their status heartbeat. The master uses all the WES status heartbeats to generate a system status heartbeat that every device in the network can hear. The slave VSCs use this system status heartbeat to monitor one or more WESs.

The system status heartbeat is a derived message that is regularly broadcast by the master VSC. It is unlikely, but possible that an error on the master could generate false information about the WESs since this is a derived message. The WESs periodically also send an encrypted message that is rebroadcasted by the master to all devices in the network. Slave VSCs use this message to verify the system status messages are correct. The slave VSCs must receive an encrypted message before enabling its outputs. This will introduce roughly one WES Encrypted Message Rate delay transitioning from Estoped to Enabled.

One or more devices in the network can be designated as Repeater / Routing Secondary Coordinator. This device provides a secondary sync message to coordinate frequency hopping and repeats any message it receives. The secondary Coordinator can be use to fill in weak coverage spots or extend the reach of the network. This device can be placed any where it will have good line of sight to the Primary Coordinator.

Configuration Terminology and Guidance

Standard Tab

TX Power Level

This is the transmit power in dbm for most radio configurations

Network ID

This is number between 1 and 4096 that should be unique for every RF network operating at your site.

Logical ID

This is the source address used for sending messages on the network. The least significant 3 bits must be unique for all WESs.

Frequency Key

This number between 0 and 14 inclusive set the pysudo random hop table. Colocated RF networks should use different keys to minimise the chance of interfearance.

Radio Setting

This defines the radio type and physical slot used. This should be set to "Slot 1 Microhard 900".

Radio Mode

The only master in the network must be the Master VSC

Wired Setting

This should be set to SRCs UART or CAN J1939 depending on the hardware configuration of your VSC. WESs should use USB.

CAN Baudrate

Set the baudrate for CAN VSCs

Advanced Tab


000-0000 for multi-point

Multi-Master Sync

Not enabled for multi-point

Max Packet Size

Helps define max packet size. Should be zero for Multipoint.

Min Packet Size

Helps define max packet size. Should be 2 for Multipoint.

RF Baud Rate

Defines how fast the radio transmits


Tells the radio many times to retransmit a packet

Radio Diagnostics

Turns on radio diagnostic reading from the master radio. Should not be used on slaves.

Multipoint Tab

Multipoint Enabled

Must be set on all devices

Master Poll Interval

Defines how often the master polls the slave WESs in the network.

WES Encryped Msg Rate

Defines how often an encrypted message is sent.

WES Encryption Key

This a 32-bit hex key that is used for message encryption between slave devices that the master can not modify without invalidating.

Associated Output ID

This logical ID of the WES that a VSC's Master Enable 2 is associated

Comms Timeout

This is the amount of time that can elapse between heartbeats from the WES before Comms Timeout estop will be generated. At the bare minimum this should be the Master Polling Rate x 8 x 3. This is a worst case timeout that is only used when the WES goes out of range. The WES will generate an asynchronous heartbeat when ever the Estop or Power button button is pressed. The longer this timeout is, the more robust the system will be to RF interference.

Encrypted Comms Timeout

This a dedicated comms timeout for encrypted messages since they are sent much less frequently.

Signal Strength Lookback

Defines the look back period for the Multipoint HB Viewer and signal strength calculations.

Care List Table

This table defines the functionality of Master Enable 1 and allows you to set the encryption key for any WES that you are monitoring. A WES can have any logical ID but when logically ANDed with 7 it will have an ID between 0-7. Master Enable 1 can be used to monitor 1 or more WESs by checking the Care checkbox. The WES's Encryption Key must be provided for any check-boxed row and for the Associated Output ID.

Configuration Instructions

TabMaster VSCSlave VSCsWESs

Network ID

StandardAll the same and less than 4096 and not 256
Logical IDStandardGreater than 7 and unique to the networkGreater than 7 and unique to the networkUnique to each WES and 0-7 inclusive
Frequency KeyStandardBetween 0 and 14 inclusive
Radio SettingStandardSlot 1 Microhard 900
Radio ModeStandardMasterSlaveSlave
Wired SettingStandardSRCS UARTUSB Serial
CAN BaudStandard250K

TabMaster VSCSlave VSCsWESs
Multi-master SyncAdvancedDisabled
Max packet sizeAdvanced0
Min packet sizeAdvanced2
RF Baud RateAdvancedMH 276480
Data RateAdvanced230400
Radio DiagnosticsAdvanced100

TabMaster VSCSlave VSCsWESs
Master Poll IntervalMultipoint3030 (Not used / Doesn't matter)0 (Enables polling mode)
WES Encrypted Msg RateMultipointNot SetableNot Setable1500
WES Encryption KeyMultipointNot SetableNot SetableHex 32-bit Typically all set the logical ID
Ex: Logical id 7: 77777777 
Associated Output IDMultipointThe ID associated with the ME0The ID associated with the ME0Not Setable
Comms TimeoutMultipoint2500
Encrypted Comms TimeoutMultipoint1600016000Not Setable
Signal Strength LookbackMultipoint1000
Care ListMultipointSet WES Encryption Keys
Set cares for ME1 
Not Setable

TabMaster VSCSlave VSCsWESs
Mesh NetworkMeshEnabled
Channel Access ModeMeshTDMA
Carrier Sense ThresholdMesh0
Aloha Repeat IntervalMesh0
Aloha SlotsMesh4
TDMA Slot NumberMesh13


RoutingMeshNot Enabled
Coordinator ModeMeshPrimary CoordinatorSlave

Example Configurations And Outputs

For each VSC, the MCU Master Enable will be de-asserted when its associated WES (set by the assoc. output ID field) is e-stopped or goes out of range. The CPLD Master Enable will be deasserted when any WES in its care list is e-stopped or goes out of range.

Single Estop or Off

WES 0 EstoppedVSC 0VSC 1VSC 2VSC 3
ME 2 - Associated1000
ME 1 - Care Group0001

WES 1 EstoppedVSC 0VSC 1VSC 2VSC 3
ME 2 - Associated0100
ME 1 - Care Group1000

WES 3 EstoppedVSC 0VSC 1VSC 2VSC 3
ME 2 - Associated0001
ME 1 - Care Group0010

Double Estop or Off

WES 1 + 3 EstoppedVSC 0VSC 1VSC 2VSC 3
ME 2 - Associated0101
ME 1 - Care Group1010

WES 2 + 3 EstoppedVSC 0VSC 1VSC 2VSC 3
ME 2 - Associated0011
ME 1 - Care Group0110

Example Config: VSC 0 through 3

Related articles

Content by Label
cqllabel = "kb-how-to-article" and type = "page" and space = "DOC"

Page Properties

Related issues