Brooks GP200 Owner's manual

RS485 L-Protocol Supplemental Manual
GP200 Series Metal Sealed
Pressure-Based Mass Flow Controllers

Contents
Contents
Section 1 Introduction
Purpose.........................................................................................................................................1
Scope ............................................................................................................................................1
Section 2 Background
Topology .......................................................................................................................................3
Communication Parameters .........................................................................................................3
Message Format ...........................................................................................................................4
Section 3 Message Protocol Details
Query for MACID .........................................................................................................................7
Digital Mode Selection ..................................................................................................................9
Query Present Control Mode......................................................................................................10
Freeze Follow .............................................................................................................................12
New Setpoint...............................................................................................................................13
Ramp Time .................................................................................................................................14
Filtered Setpoint..........................................................................................................................17
Indicated Flow.............................................................................................................................19
Valve Drive Current ....................................................................................................................21
Calibrated Instance (Process Gas) Selection.............................................................................23
Query for Calibration Instance (Process Gas) Selection ............................................................24
Query for Available Calibration Instance ....................................................................................26
Auto Zero Enable/Disable ...........................................................................................................28
Requested Zero Enable ..............................................................................................................29
Query for Requested Zero Status ...............................................................................................30
Query for Sensor Current Zero...................................................................................................32
Query for Sensor Reference Zero ..............................................................................................34
Set Sensor Reference Zero ........................................................................................................36
Set Default Control Mode............................................................................................................37
Query Default Control Mode .......................................................................................................38
Query for Inlet Pressure .............................................................................................................40
Query for Temperature ...............................................................................................................42
Section 4 Software Design Requirement
Normal Transaction Scenarios......................................................................................................45
Read Transaction Scenario .........................................................................................................45
Write Transaction Scenario .........................................................................................................46

Contents
Abnormal Transaction Scenarios..................................................................................................46
Read Transaction Scenario ..........................................................................................................46
Packet Error .................................................................................................................................46
Read Error ...................................................................................................................................47
Write Transaction Scenario ..........................................................................................................48
Packet Error .................................................................................................................................48
Write Error....................................................................................................................................48
Protocol Timing .............................................................................................................................49
Message Seque nce between Master Controller and a M FC Slave Controller .................................... 50
MFC New Setpoint Conversion.....................................................................................................51
Sensor Zero Filter..........................................................................................................................51
Requested Zero ............................................................................................................................52
Auto Zero ......................................................................................................................................52
Calibration Instances.....................................................................................................................53
Analog / Digital Mode ....................................................................................................................53
Appendix: Tool - Device Communication ......................................................................................55

Section 1 - Introduction
Introduction
Purpose
The purpose of this document is to outline the generic RS485 multi-drop
communication protocol for the GP200 Series Pressure-Based MFCs.
Scope
This protocol is intended to serve all digital MFCs. Only the following
messages are supported:
• Query for MAC – Master controller will use this message to query the
existence of a MFC controller.
• Digital mode selection – Master controller will use this message to set a
MFC controller to digital mode.
• Freeze Follow – Master controller will use this message to configure a
MFC controller to act upon a new set point when received.
• Set Point – Master controller will use this message to send a new set
point to a MFC controller.
• Ramp Time – Master controller will use this message to send a ramp
time to a MFC controller.
• Filtered Set Point – Master controller will use this message to get the
current set point from a MFC controller.
• Indicated Flow - Master controller will use this message to get the current
flow reading from a MFC controller.
• Valve Drive Current - Master controller will use this message to get the
valve drive current.
• Calibration Instance (Process Gas) Selection - Master controller will use
this message to select which calibration instance is to be used for flow
metering.
• Query for Calibration Instance (Process Gas) Selected - Master
controller will use this message to query the selected calibration
instance, which is currently being used for flow metering.
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Section 1 - Introduction
• Query for Available Calibration Instances (Process Gases) - Master
controller will use this message to query available number of calibration
instances.
• Auto Zero Enable/Disable - Master controller will use this message to
enable auto zero function.
• Requested Zero Enable - Master controller will use this message to
enable requested function.
• Query for Requested Zero Status – Master controller will use this
message to query if the requested zero function has been completed.
• Query for Sensor Current Zero - Master controller will use this message
to query the current sensor zero offset.
• Query for Sensor Reference Zero - Master controller will use this
message to query the sensor reference zero offset.
• Set Sensor Reference Zero - Master controller will use this message to
set sensor reference zero offset.
• Query for Inlet Pressure – Master controller will use thismessage to
query the pressure transducer reading.
• Query for Temperature – Master Controller will use this message to
query the temperature reading
2

Section 2 - Background
Background
Topology
The controller acts as a Master device on an RS-485 multi-drop bus. It
controls all transactions on the bus.
The digital MFC controller (up to 31) acts as a slave device on an RS-485
multi-drop bus. It continually listens for transaction requests from the Master
controller, processes requests addressed to it, and sends replies as needed.
Communication Parameters
• BAUD rate: 9600, 19200, 38400, 57600
• Data bits: 8 Start bit: 1 Stop bit: 1 Parity: none
• Byte order: LSB first
• MAC(Address) assignment:
• Master controller: 0
• Digital MFC controller 1-31: 0x21(33) – 0x3F(63)
• Broadcast packet address: 0xFF(255)
• Addresses 0x01 to 0x1f are reserved for bus control characters
• ACK – 0x06
• NAK – 0x16
3

Section 2 - Background
Message Format
Messages on the bus are sent as packets with a fixed format, illustrated as
the following diagram. Each packet begins with the target digital MFC
controller MAC ID (address), an STX character (0x02), a service (command)
code (0x80 for read and 0x81 for write), a packet length character, a
variable identifier (consisting of Class ID, Instance ID, Attribute ID) and a
data count between 0 to 2. Each packet ends with a pad byte of 0, and a 1-
byte checksum, which is the sum of all of the bytes in the packet, other than
the target MAC ID, modulo 256. The checksum calculation discards the
carry from the byte summation calculation. This message structure
resembles with the one used by DeviceNet protocol.
MAC ID (Targeted MFC Controller Address)
STX(0x02)
Command Code(0x80 for read, 0x81 for write)
Packet Length
Class ID
Instance ID
Attribute ID
Data(0 - 2 bytes)
Pad(0x00)
Checksum
All communication on the bus is done by service requests (from Master
controller to a specified MFC slave controller), each addressed to a specific
MAC ID, Class ID, Instance ID and Attribute ID. Currently this protocol
supports only 2 services – Read and Write.
All communication on the bus is done by service requests (from Master
controller to a specified MFC slave controller), each addressed to a specific
MAC ID, Class ID, Instance ID and Attribute ID. Currently this protocol
supports only 2 services – Read and Write.
The following table summarizes the specification of Class ID, Instance ID
and Attribute ID for each supported message:
4

Section 2 - Background
Message
Class ID
Instance ID
Attribute ID
Query for MAC ID
0x03
0x01
0x01
Digital Mode Selection
0x69
0x01
0x03
Query for Present Control Mode
0x69
0x01
0x03
Freeze Follow
0x69
0x01
0x05
New Setpoint
0x69
0x01
0xA4
Ramp Time
0x6A
0x01
0xA4
Filtered Setpoint
0x6A
0x01
0xA6
Indicated Flow
0x6A
0x01
0xA9
Valve Drive Current 0x6A 0x01 0xB6
Calibration Instance
0x66
0x00
0x65
Query for Calibration Instance
0x66
0x00
0x65
Query for Available # of Calibration Instances
0x66
0x00
0xA0
Auto Zero Enable/Disable 0x68 0x01 0xA5
Requested Zero Enable
0x68
0x01
0xBA
Query for Requested Zero Status
0x68
0x01
0xBA
Query for Sensor Current Zero
0x68
0x01
0xA9
Query for Sensor Reference Zero
0x68
0x01
0xAA
Set Sensor Reference Zero
0x68
0x01
0xAA
Set Default Control Mode
0x69
0x01
0x03
Query for Default Control Mode
0x69
0x01
0x03
Query for Inlet Pressure
0x31
0x02
0x06
Query for Temperature
0x31
0x03
0x06
Set MAC ID (Hardware Dependent): See Appendix
0x03
0x01
0x01
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Section 3 - Message Protocol Details
Message Protocol Details
The following sub-sections describe in detail the supported messages.
Query for MAC ID
Master controller will use this message to query the existence of a MFC
controller.
Query message from Master controller to a digital MFC controller
MAC ID (Targeted MFC controller address)
STX(0x02)
Command Code(0x80 for read)
Packet Length(0x03)
Class ID(0x03)
Instance ID(0x01)
Attribute ID(0x01)
Pad(0x00)
Checksum(0x8A)
7

Section 3 - Message Protocol Details
Response message from a digital MFC controller to Master controller
MAC ID (0 – Master controller)
STX(0x02)
Command Code(0x80 for read)
Packet Length(0x04)
Class ID(0x03)
Instance ID(0x01)
Attribute ID(0x01)
MFC MAC ID
Pad(0x00)
Checksum
8

Section 3 - Message Protocol Details
Digital Mode Selection
Master controller will use this message to set a MFC controller to digital or
analog mode.
MAC ID (Targeted MFC controller address)
STX(0x02)
Command Code(0x81 for write)
Packet Length(0x04)
Class ID(0x69)
Instance ID(0x01)
Attribute ID(0x03)
Mode(1 – digital, 2 - analog)
Pad(0x00)
Checksum
9

Section 3 - Message Protocol Details
Query Present Control Mode
Master controller will use this message to query the present control mode.
MAC ID (Targeted MFC controller address)
STX(0x02)
Command Code(0x80 for read)
Packet Length(0x03)
Class ID(0x69)
Instance ID(0x01)
Attribute ID(0x03)
Pad(0x00)
Checksum(0xF2)
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Section 3 - Message Protocol Details
Response message from a digital MFC controller to Master controller
MAC ID (0-Master Controller)
STX(0x02)
Command Code(0x80 for read)
Packet Length(0x04)
Class ID(0x69)
Instance ID(0x01)
Attribute ID(0x03)
Mode(1 – digital, 2 - analog)
Pad(0x00)
Checksum
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Section 3 - Message Protocol Details
Freeze Follow
Master controller will use this message to configure a MFC controller to act
upon, or ignore, a new set point when received.
MAC ID (Targeted MFC controller address)
STX(0x02)
Command Code(0x81 for write)
Packet Length(0x04)
Class ID(0x69)
Instance ID(0x01)
Attribute ID(0x05)
FreezeFollow(1–Act on new set point immediately-(default))
(0-Ignore change in set point)
Pad(0x00)
Checksum
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Section 3 - Message Protocol Details
New Setpoint
Master controller will use this message to send a new set point to a MFC
controller.
MAC ID (Targeted MFC controller address)
STX(0x02)
Command Code(0x81 for write)
Packet Length(0x05)
Class ID(0x69)
Instance ID(0x01)
Attribute ID(0xA4)
Data Byte#1(LSB)*
Data Byte#2(MSB)*
Pad(0x00)
Checksum
*See New Setpoint conversion Table, pg. 51
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Section 3 - Message Protocol Details
Ramp Time
Master controller will use this message to send a ramp time to a MFC
controller. The ramp time is how long the MFC controller should take to
reach the final set point from the current set point. The unit is millisecond. A
zero ramp time effectively disables the ramping.
Request message from Master controller to a digital MFC controller
MAC ID (Targeted MFC controller address)
STX(0x02)
Command Code(0x81 for write)
Packet Length(0x05)
Class ID(0x6A)
Instance ID(0x01)
Attribute ID(0xA4)
Data Byte#1(LSB)
Data Byte#2(MSB)
Pad(0x00)
Checksum
Ramp time (msec)
Ramp Time value (hex)
0
0000
65535
FFFF
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Installation and Operation Manual
Query for Ramp Time Setting
Master controller will use this message to query the ramp time setting
Request message from Master controller to a digital MFC controller
MAC ID (Targeted MFC controller address)
STX(0x02)
Command Code(0x80 for read)
Packet Length(0x03)
Class ID(0x6A)
Instance ID(0x01)
Attribute ID(0xA4)
Pad(0x00)
Checksum (0x94)
15

Section 3 - Message Protocol Details
Request message from Master controller to a digital MFC controller
MAC ID (0 - controller address)
STX(0x02)
Command Code(0x80 for read)
Packet Length(0x07)
Class ID(0x6A)
Instance ID(0x01)
Attribute ID(0xA4)
Data Byte #1(LSB)
Data Byte #2(MSB)
Reserved Byte #1
Reserved Byte #2
Pad(0x00)
Checksum
16

Section 3 - Message Protocol Details
Filtered Setpoint
Master controller will use this message to get the current set point from a
MFC controller. This is the current set point after ramping has been applied.
Request message from Master controller to a digital MFC controller
MAC ID (Targeted MFC controller address)
STX(0x02)
Command Code(0x80 for read)
Packet Length(0x03)
Class ID(0x6A)
Instance ID(0x01)
Attribute ID(0xA6)
Pad(0x00)
Checksum (0x96)
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Section 3 - Message Protocol Details
Response message from a digital MFC controller to Master controller
MAC ID (0 – Master controller)
STX(0x02)
Command Code(0x80 for read)
Packet Length(0x05)
Class ID(0x6A)
Instance ID(0x01)
Attribute ID(0xA6)
Data Byte #1(LSB)*
Data Byte #2(MSB)*
Pad(0x00)
Checksum
*SeeNew Setpoint Conversion Table Pg. 51
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