Honeywell CM4 User manual

CM4 Serial Communication Protocol
Operating Instructions

CM4 Protocol License Agreement
Carefully review the following terms and conditions before proceeding.
In the event that you do not agree to these terms and conditions, you must
return this package intact. By not returning this package you indicate your
acceptance of all terms and conditions stipulated herein. Furthermore,
retaining it indicates and acknowledges that you have read this agreement,
understand it, and agree to its terms and conditions.
LICENSE
Honeywell Analytics grants to the user, in exchange and in consideration
for applicable fees, a license for the use of the CM4 protocol, the right to
use and the CM4 protocol denition of which is supplied to you in a
separate document. This license grants you the right of knowledge and
use of the CM4 protocol. This license does not grant ownership of the
subject. This license agreement is for site license only.
In Honeywell Analytics' granting and the user’s acceptance of this license,
this license agreement is binding. This license is granted to you, the
purchaser, and you may not sublicense, transfer or assign this license.
You may not transfer, copy or divulge any part of this protocol technique or
knowledge except as expressly provided for in this agreement.
Honeywell Analytics considers the CM4 protocol proprietary to itself.
TERM
This agreement shall be in effect until terminated. Either party may
terminate this agreement through written notication. All materials relating
to this agreement shall be returned to Honeywell Analytics upon the
termination of this agreement.
WARRANTS
Honeywell Analytics warrants this package to the extent as is set forth in
the CM4 protocol document and any other supplied documentation.
Honeywell Analytics disclaims all warranties not explicitly stated within
this agreement. Honeywell Analytics does not warrant the operation will
be uninterruptible or error-free. Furthermore, Honeywell Analytics does
not guarantee the CM4 protocol will meet your requirements. The use and
results the USER obtains are the responsibility of the USER.
In no event will Honeywell Analytics or its suppliers or vendors be liable to
you or any other person for any damages, expenses, interruption of
business, or other damages arising out of use or the inability to use the
CM4 protocol.
NOTE:
CM4 refers to any of the CM4 instruments Honeywell Analytics has
designed and markets, and is the trademark of the family.

Contents
Introduction 1
Overview 1
Glossary 2
Communication Port 3
Set up Procedure 4
Protocol Specics 5
Data and Packets 5
Checksum (Check Character) 6
ACK/NAK Handshake 7
Protocol Packet Definition 8
Packet Format 8
Start Code 8
Receiver Address 8
Transmitter Address 8
Length 8
Command 8
Data 8
Checksum 8
Date Format 9
Time Format 9
Date/Time Examples 9
Concentration Data Format Code 9
Generic Responses 10
ACK - 0x20 10
NAK - 0x21 10
Bad CMD - 0x66 10
Unknown CMD – 0x67 10
Protocol Command Definition 11
Status and Query Commands 11
NOP - 0x28 11
Get System Information – 0x30 11
Get Unit Status – 0x31 12
Get Idle Time - 0x32 15
Get Date & Time - 0x33 15
Get Maintenance Dates - 0x34 16
Get Point Conguration - 0x35 17
Get Alarm History - 0x36 18
Get Current Point Status - 0x37 19
Get TWA Time - 0x38 20
Get Display Cycle Time - 0x39 20
Get the Number of Gas Tables Available - 0x3A 21
Get Printer Setup - 0x3B 21
Get Gas Table Data - 0x3C 22
Get Fault History - 0x3D 23
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Get K-Factor - 0x3E 24
Get Pyrolyzer Temperatures - 0x42 25
Get Pump Limits - 0x43 25
Get Filter Life - 0x44 26
Get Floating Status - 0x45 27
Get One Alarm - 0x47 29
Configuration 30
Set K-Factor - 0x50 30
Reset Fault or Alarm - 0x51 31
Set Key-Code - 0x52 32
Lock Keyboard - 0x53 33
Set 2mA Fault Operation - 0x54 33
Start New Cycle - 0x55 34
Program Chemcassette Counter - 0x56 34
Set Printer Conguration - 0x57 35
Set Point Enable/Disable - 0x58 36
Set Point Conguration - 0x59 37
Set TWA Time - 0x5A 38
Set Display Cycle Time - 0x5B 38
Set Idle Time - 0x5C 39
Set Date Format - 0X5D 39
Set Date and Time - 0x5E 40
Set Relay State - 0x5F 41
End Point Lock On - 0x60 42
Start Point Lock On - 0x61 42
Save Current Conguration - 0x62 43
Restore Conguration - 0x63 43
Set Duty Cycle - 0x65 44
Set Filter - 0x66 45
Get Duty Cycle - 0x69 46
Operation 47
CM4 Instrument 47
Commands 47
Responses 47
Example Packets 48

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Introduction
Overview
The CM4 serial communications protocol was designed and developed
by Honeywell Analytics, and is proprietary information. This manual will
describe the setup and operation of the communication protocol.
Your CM4 four-point continuous monitor is equipped with an
optional serial remote device communication port. With this
communication port, you can monitor the CM4 system’s operation with
equipment from a remote location. It will also allow you to gather gas
concentration data for analysis or reports.
The CM4 monitor accepts commands and issues responses to any valid
command it receives. The CM4 monitor is always considered the “slave”
device, and the remote equipment is the “master” device. The remote
equipment can be a personal computer (PC), a programmable logic
controller (PLC), or other device capable of RS-232, RS-422, or RS-485
serial communications. This conguration requires a “master” device.
Therefore, one CM4 monitor will not communicate directly with another
CM4 monitor. However, one master can be used to communicate with
more than one CM4 monitor on a two-wire RS-485 bus.
The CM4 monitor supports multiple baud rates. These user selectable
rates are 1200, 2400, 4800, 9600, and 19,200. Additional port settings
are 8-bit, 1 stop bit, and no parity.
The slave is identied by an address programmed into the CM4 monitor
(selectable 1-255). If more than one CM4 monitor is used, each must
have a unique address.
The equipment (master) is always at address 0. Each CM4 monitor will
respond to a signal directed to it from the equipment. To prevent a
collision of messages, the master must avoid transmitting any
information after a packet until the slave responds. Typically this occurs
within 1000 milliseconds.

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Glossary
The following terms are used in this manual:
Byte: A byte is a collection of 8 bits (or pieces) of information used in the
communication process. A byte refers to these 8 bits as a single entity.
Each bit has a value of either 0 or 1.
Communication: The act or process of passing digital information
between two points.
Data: Information that is transferred between the equipment and the CM4
monitor. Data refers to the information contained within a packet (see
Packet). This information may be gas concentration, date, or other
information.
Equipment: This term is used to refer to the master device which is used
to communicate with the CM4 monitor(s). The equipment can be a
personal computer (PC) or other device capable of performing the digital
communications described in this protocol.
Handshake: The process of acknowledging a communication has been
received. The CM4 monitor uses ACK/NAK responses.
Hexadecimal: A type of numbering system with a base of 16. In this
numerical system, numbers 10 through 15 are represented by the letters
A through F respectively. The shortened version of the word hexadecimal
is generally "Hex," as in "Hex 42." "0x" is the notation used in this manual
for hexadecimal (e.g. 0x42).
Instrument: This term is used to refer to the CM4 four-point continuous
monitor.
Master: Another computer which communicates with slaves using the
CM4 protocol.
Packet: A block of information that is passed between the instrument and
the equipment. A packet is made from many bytes of information.
Protocol: The manner in which data is transferred and the format used
for the transfer. CM4 protocol refers to the packets of transferred data the
CM4 instrument recognizes.
Slave: The MDA Scientic CM4 gas monitor. A network may have several
slaves.
Time-Out: The maximum amount of time allowed between the time the
last byte of a packet is sent from the “master” device to the time the
“slave” device responds. The time-out period for this protocol is one
second.

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Communication
Port
Access to the CM4 protocol is through the COM port. This port is a DB-9
female connector. This port is designed for bidirectional communications
between the CM4 instrument and your equipment. Signals present at the
port conform to RS-232, RS-422, or RS-485 specications. Again, this is
based on which interface option was installed in your CM4 instrument.
The pin-out specications for each option are as follows:
RS-232 (Part Number 874270)
Pin Number Signal
2Transmit
3Receive
5Ground
RS-422 (Part Number 874326)
Pin Number Signal
2Receive +
3Receive -
4 Transmit -
5Transmit +
RS-485 (Part Number 874556)
Pin Number Signal
2 B (Transmit/Receive +)
3 A (Transmit/Receive -)
7Signal Ground

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Set up
Procedure
After the networking cabling has been connected to the slave, the
slave must be congured to communicate. Baud rate, address, and
protocol version are selectable. Conguration is performed with the
following sequence:
<PROGRAM> <1> is pressed to stop monitoring.
SELECT PROGRAM < >
The keys 3 3 1 are pressed to go to the COM port setup menu.
SET COM PORT
One of the four protocol congurations must be selected.
COM PORT DISABLED
or
COM PROTOCOL VER 1
or
COM PROTOCOL VER 2
or
COM PROT. LONWORKS
Protocol 1 is recommended for compatibility with existing master
computers. Protocol 2 provides superior data integrity, but requires a
change to the master. LONWORKS requires extra hardware.
The selection is made by pressing <ENTER>.
COM PORT 9600 BAUD
Baud rates of 1200, 2400, 4800, 9600, and 19200 are available. 9600
baud is recommended for most applications. The selection is made by
pressing <ENTER>.
SET INST. ADDRESS
INST. ADDRESS 001
Every slave on a network must have a unique address from 1 to 255.
If only one slave is present, this value may remain at 1. After entering
a unique number, press <ENTER>.
After these steps the COM port setup is complete. Normal operation is
restored by pressing <MONITOR>

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Protocol
Specics
The protocol has been designed for exibility and efciency. This byte-wise
protocol communicates information by transferring bytes of data back and
forth between master and slave. A group of bytes for each communication
is called a packet.
The master and slave(s) transfer information via data packets.
These packets will always contain bytes to start communication, an
address, a packet length, a command, and a checksum.
Additional optional variable-length data bytes or optional parameters
can also be sent or received. This section is a brief overview of the
protocol specics.
Data and Packets
A byte is a piece of data. It is a way to indicate information
and is composed of eight bits of information. A bit is
the smallest possible piece of information. It can only
be two possible values, 1 or 0 (True or False). A byte can
have a decimal value from 0 to 255. In hexadecimal
representation, a byte's value can range from 0x00 to 0xFF.
Hexadecimal representation will be used for the remainder of
this manual. The number may be interpreted in a manner
other than a number, for example, as a letter.
Using ASCII characters, where 0x41 is the letter A, 0x42 is
the letter B, 0x43 is C, and so on, a message can be written
as these numbers. Each number is a byte. For example, the
word "BAD" is 0x42, 0x41, 0x44.
The collection of the three bytes in our message (0x42, 0x41,
0x44) may be referred to as a packet, since these bytes are
always associated with each other.
Just as all words are not the same length (number of letters),
packets may also vary in length. One way to denote the size
of the word is to put the number of letters you have in the
word as the first number in your packet. Your data packet
containing the word (or command) "BAD" will then become
0x03, 0x42, 0x41, 0x44.

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Checksum (Check Character)
During transmission of the packet, an error could change
the value of the data. Suppose in our example, for instance,
the packet 0x03, 0x42, 0x41, 0x44 is actually 0x03,
0x42, 0x30, 0x44. How can you determine that the numbers
you get are the same as the numbers sent? Using a
check-character is a method of assigning a value to the
packet to check if any of bytes have been modified.
If all the data bytes are added together and this sum made
into a byte, that byte could be called a check character, or
more commonly referred to as a checksum. For the CM4
instrument, the checksum is the negated sum of all the bytes
in the packet. In our example, the packet is 0x03, 0x42,
0x41, 0x44, 0x36. For this packet, the sum modulo 0x100
of all the bytes added to the checksum must equal zero (0).
Any other result indicates there is an error with the data.
The slave's data contained within the packet is interpreted in
a somewhat different manner than our example. The data is
composed of two sections, a command and one or more
parameters. The command indicates what type of
information is being transmitted in the packet.
The parameters contain specific arguments or data values
to be interpreted. Parameters for most CM4 instrument's
packet require at least four bytes for the Date and Time
stamps. This information is important to provide a date and
time reference for each communication from the instrument.
You should ensure that the date and time have been set
accurately in each CM4 monitor.
Every packet sent by the CM4 instrument also contains an
address, a length, a command and its associated
parameters, and a checksum. The CM4 instrument assumes
that the master's address is 0 (zero). You assign a unique
address to each slave which communicates with
the master.

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ACK/NAK Handshake
Each slave (CM4) uses a handshake scheme between itself
and the master. The simplest response back from the
instrument is called an ACK (an abbreviation for
ACKnowledge). When the slave receives a command packet
from the equipment, it will send back an ACK response if
the command is received, but no additional data has been
requested in the command.
If however, the checksum does not match, the slave will send
a NAK (an abbreviation for Negative AcKnowledge). A NAK
indicates that a data packet has been received, but the
checksum did not match with the packet data. The master
may send the request again. An example of an ACK packet
is 0x40, 0x00, 0x05, 0x20, 0x9B (40 + 0 + 5 + 20
+ 9B = 0x100).

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Protocol Packet Denition
Packet Format Two similar protocols are supported by CM4 software.
The original protocol with a minimum packet length of ve
bytes is included for compatibility with previous software.
Additionally, a new protocol with a minimum packet length
of six bytes is included for greater robustness.
Examples of packets using both protocols are included at
the end of this book.
The format of packets using original version 1 protocol is
as follows:
The format of packets using the new version 2 protocol
is similar:
Start Code Size: 1 byte. Always 0x40
Receiver Address Size: 1 byte
For responses from slave to master,
this is always 0. For inquiries from
master to slave, this must match the
slave’s address as set with menu
function 3.3.1.
Transmitter Address Size: 1 byte
For inquiries from master to slave,
this is always 0. For responses from
slave to master, this will match the
slave’s address as set with menu
function 3.3.1.
Length Size: 1 byte
The length of the total packet
from start code to checksum.
Command Size: 1 byte
This is 0x28 to 0x69 as dened in
the remainder of this book.
Data Size: 0-250 byte(s)
This section varies according to the
command chosen and is often
empty.
Checksum Size: 1 byte
The two’s complement of the sum of
all the previous bytes in the packet.
This makes the sum of the entire
packet a multiple of 0x100.
start code receiver
address length command data checksum
start code receiver
address
transmitter
address length command data checksum

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Generic Data Formats
Date Format 2 bytes
Year: (7 bits)
Month: (4 bits)
Day: (5 bits)
Year is based from 1980. 1989 would be
89 - 80 = 9.
Time Format 2 bytes
Hours: (5 bits)
Minutes: (6 bits)
Seconds/2: (5 bits)
Date/Time Date: 1F 56 Oct. 22. 1995
Examples: Date: 1F 75 Nov. 21, 1995
Time: 13 C0 02:30:00
Time: 74 23 14:33:06
Time: 4C 09 09:32:18
Concentration U0XXXYYY
Data Format
Code U = 0 concentration of PPB
1 concentration of PPM
0 = future use
XXX = future use
YYY = used for PPB/PPM (bit 7), and indicates
where the decimal place is located:
000 = no decimal places
001 = 1 decimal place
010 = 2 decimal places
011 = 3 decimal places
For example, (HEX) 82 (1000 0010)
represents PPM with 2 decimal places.
For a concentration value of 317:
Format Code Interpretation
0000 0010 (02) 3.17 PPB
1000 0010 (82) 3.17 PPM
0000 0000 (00) 317 PPB

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Generic Responses
The CM4 monitor will return generic responses to the equipment if
there is not a specic response dened, or if there is a problem in the
communication transactions. There are four generic responses. Each of
these response packets are 5 bytes, and contain only the start byte,
address, length command code, and checksum.
ACK - 0x20 This is used for an acknowledgement of
a command.
NAK - 0x21 This is used for a negative acknowledgement of
command. The last received command had an
incorrect checksum.
Bad CMD - 0x66 This is sent to the master when the command
is expected or is not appropriate for the
current state.
Unknown CMD - This response is sent by the slave when a 0x67
command is not recognized.

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Protocol Command Denition
Status and Query Commands
These commands indicate the function and expected response format
for each command. Command numbers are in hexadecimal. If a
specic response is required, the response packet will have the same
command code as the command packet sent to the slave. If no specic
response packet is specied, a general ACK response is sent to
acknowledge the command.
NOP - 0x28 This is used to test for communication between the
master and the specied slave.
Command packet to instrument:
Command Code (0x28) - 1 byte
Get System This packet requests information about the slave system
Information only and the software version currently in use.
0x30
Command packet to instrument:
Command Code (0x30) - 1 byte
Response packet from instrument:
Command Code (0x30) - 1 byte
CM4 Date - 2 bytes
CM4 Time - 2 bytes
Serial # - 2 bytes, product code 851 is assumed.
Software Rev.
Major - 1 byte
Minor - 1 byte
VIP - 2 bytes - 0xFFFF as default
Prom Check Sums
MSB PROM - 2 bytes
LSB PROM - 2 bytes
Status - 1 byte
0x00 Read veried
0xff Error in reading
Software Rev. Examples (Major/Minor/VIP):
01/07/FFFF - Rev. 1.07
03/0C/FFFF - Rev. 3.12
03/0C/0066 - Rev. 3.12-102
04/12/017A - Rev 4.18-378

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Get Unit Status This command requests the current condition or
0x31 status of the slave. This command allows the
master to inquire about the general operating
condition of the system.
Command packet to instrument:
Command Code (0x31) - 1 byte
Response packet from instrument:
Command Code (0x31) - 1 byte
CM4 Date - 2 bytes
CM4 Time - 2 bytes
General Status - 2 bytes
bit 0: Current Operating mode
0 = Not monitoring
1 = Monitoring
bit 1: Keyboard Lockout state
0 = Disabled
1 = Enabled
bit 2: Key pad status
0 = unlock
1 = locked
bit 3: Chemcassette counter status
0 = Counter disabled
1 = Counter enabled
bit 4: 2mA Fault operation
0 = Feature disabled
1 = Feature enabled
bit 5: Point Lock-ON
0 = No Lock-ON
1 = Lock-ON
bits 6-7: Point Locked (Ignore if bit
5 is 0.)
00 = Point 1
01 = Point 2
10 = Point 3
11 = Point 4
bit 8: Date Format
0 = MM/DD/YY
1 = DD/MM/YY
bits 9-12: Points enable when No
Lock on
0x01 = Point 1 enabled
0x02 = Point 2 enabled
0x04 = Point 3 enabled
0x08 = Point 4 enabled
(continued)

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(Get Unit Status bit 13: Relay state
0x31, continued) 0 = De-energized
1 = Energized
bit 14: Relay Latching state
0 = Non-latching
1 = Latching
bit 15: Alarm Simulation state
0 = Unit not in alarm
simulation mode
1 = Unit in alarm simulation
mode
New Events - 1 byte
bit 0: The alarm history contains an
entry which has not been read via
packet 0x36 or 0x47.
1 = a new entry exists
0 = no new entries
bit 1: The fault history contains an
entry which has not been read via
packet 0x3D
1 = a new entry exists
0 = no new entries
bits 2-7: undened
Concentration Summary - 1 byte
bits 0-1: concentration summary
integer (CSI) for point 1
bits 2-3: CSI for point 2
bits 4-5: CSI for point 3
bits 6-7: CSI for point 4
The CSI expresses the concentration
relative to the alarm levels according to the
following enumeration:
0 0.0 == concentration
1 0.0 < concentration < AL1
2 AL1 <= concentration < AL2
3 AL2 <= concentration
Chemcassette windows remaining - 2 bytes
Chemcassette days remaining - 2 bytes
Internal Filter 2 bytes (days in use)
External Filter - 2 bytes (days in use)
Flow Rate Point 1 - 2 bytes (cc/Min)
Flow Rate Point 2 - 2 bytes
Flow Rate Point 3 - 2 bytes
Flow Rate Point 4 - 2 bytes
(continued)

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(Get Unit Status Optics Cal Status - 1 byte
0x31, continued) bit 0: Optics have been calibrated
0 = Not Tested
1 = Tested
bits 1-4: Optics test results
0x01 = Passed optics 1
0x02 = Passed optics 2
0x04 = Passed optics 3
0x08 = Passed optics 4
bits 5-7: Undened
Maintenance Status
0x01 = low ow point 1
0x02 = low ow point 2
0x04 = low ow point 3
0x08 = low ow point 4
0x10 = low Chemcassette
tape
0x20 = Maint. Relay
0x40 = Instr. Fault Relay

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Get Idle Time This command inquires about how long the unit can be
0x32 left out of analysis before setting an Instrument Fault.
Idle time is used to notify operators that the unit is not
monitoring. An idle time of 0 disables this option.
Command packet to instrument:
Command Code (0x32) - 1 byte
Response packet from instrument:
Command Code (0x32) - 1 byte
CM4 Date - 2 bytes
CM4 Time - 2 bytes
Idle Time - 1 byte (0 disabled, 1-45 minutes)
Status - 1 byte
0x00 = No errors in reading
0xff = Error in reading
Get Date & Time This command retrieves the current date and time from
0x33 the unit.
Command packet to instrument:
Command Code (0x33) - 1 byte
Response packet from instrument:
CM4 Date - 2 bytes
CM4 Time - 2 bytes
Status - 1 byte
0x00 = Date and Time READ
0xff = Read problem