CDN36X User Manual
revision 1.30
Synchronization
There are four independent processes operating in a CDN36X gateway application. The first
process is the exchange of input and output data between the user application program and the
DeviceNet master. The second process is the exchange of input and output data between the
gateway and DeviceNet master, using Polled or Change-of-State I/O messaging. The third
process is receiving serial messages and converting it to input data. The fourth process is
converting output data and transmitting it as serial messages. To ensure that no information is
lost between the gateway’s serial channel and the user application program, the CDN36X
incorporates a receive synchronization feature and a transmit synchronization feature.
I/O Exchange between
DeviceNet Master and
Application
I/O Exchange between
CDN36X gateway and
DeviceNet Master
Convert serial message
into Input Data
Input File
Inputs
DeviceNet I/O Response
Receive Synchronization
The gateway receive synchronization feature is optional for each
Serial Receive Object
instance.
It is enabled by the
Sync Enable
attribute. When enabled, the instance will not process a new
message packet until the last
Receive Data
value has been read and acknowledged by the
application program. When a
Serial Receive Object
Instance updates its
Receive Data
value, it
also toggles its
Receive Toggle
bit to indicate a new data value is available. The user application
monitors the
Receive Toggle
bit, and reads the Instance’s
Receive Data
value when the bit
changes state. Once the application has read and processed or stored the new
Receive Data
value, it acknowledges receipt by setting the Instance’s
Receive Acknowledge
bit equal to the
Receive Toggle
bit. The Instance is now able to start processing the next serial message packet.
The
Receive Toggle
and
Receive Acknowledge
bits are set to 0 at power-up.
CDN36X
Gateway
DeviceNet
Master
Application
Program
Output File
Serial
Device
DeviceNet network
Outputs
Receive
Message Packet
Transmit
Message Packet
DeviceNet I/O Command
output data
input data
Convert Output Data
into serial message
MKS Instruments, Inc.
D.I.P. Products Group
25