CDN36X User Manual
revision 1.30
Flow Control –
Selects the method of flow control used across the serial interface.
NONE
means there is no flow control over the serial data exchange. The transmitting device can
overflow the receiving device’s buffer.
XON/XOFF
is a software flow control option. Receiving device sends an XOFF character to the
transmitting device when its buffer is full, stopping further transmission. It sends an XON
character when it can again receive data. The XOFF and XON characters are not saved as
message data.
CTS/RTS
is an RS232 hardware flow control option, available only on the CDN366 gateway.
The RTS is an output and CTS is an input signal. The gateway keeps RTS active (low) when it
can receive data. It only transmits data when CTS is active (low).
Delimiter Mode –
Defines how the gateway determines when it has received a message packet.
The three delimiter modes are
List
,
Timeout
, and
Length
. Setting the appropriate bit in the
Delimiter Mode
byte selects the respective mode. The
Delimiter Mode
byte defines bits 0, 1, 2
only. Set the remaining bits 3 through 7 to zero.
List
mode is used when a message packet is framed by a specific strings of
Pre-Delimiter
and
Post-Delimiter
bytes. The
Pre-Delimiter
signals the start of a new packet. The
Post-Delimiter
indicates the end of the packet. Each
Pre-Delimiter
and
Post-Delimiter
string can be from 1 to 9
bytes in length. When the gateway receives the
Pre-Delimiter
string, it saves the subsequent
data bytes until the
Post-Delimiter
string is received. The
Pre-Delimiter
and
Post-Delimiter
bytes are not saved in the message packet. The following is a simple ASCII message example.
[STX] [data1] [data2] … [dataN] [ETX] [CR]
Pre-Delimiter
Message Packet
Post-Delimiter
Length
mode is used when every message packet contains the same number of bytes. The
Packet
Length
attribute defines the packet size, from 1 to 128 bytes. The gateway saves serial
bytes until it receives the specified number, and saves them as one message packet.
Timeout
mode uses a delay between received data bytes to determine the end of a message
packet. The
Packet Timeout
attribute defines the time-out period, from 1 to 255 milliseconds.
Pre-Delimiter List –
Required for
List Mode
. Enter a string of 1 to 9 bytes that defines the start
of a new serial message. Use Short_String data format, with 1
st
byte = string length. Example
Pre-Delimiter
is [ 0x01 0x02 ], where string length is 1 and delimiter character is 0x02 (STX).
You must use the RSNetworx
™
Class Instance Editor (Set Attribute Single command) to write a
Short_String attribute value.
Post-Delimiter List –
Required for
List Mode
. Enter a string of 1 to 9 bytes that defines the end
of a serial message. Use Short_String data format, with 1
st
byte = string length. Example
Post-
Delimiter
is [ 0x02 0x0D 0x03 ], where string length is 2 and delimiter characters are 0x0D (CR)
MKS Instruments, Inc.
D.I.P. Products Group
32
