ToolLink User Manual
MKS Instruments, Inc.
Page 11 of 30
The first 4 output data bytes received from the DeviceNet master contain used to control and monitor the
flow of data through the gateway. The remaining output data bytes contain serial message data to be
transmitted out the serial channel.
The ToolLink Gateway can receive serial message packets up to 68 bytes long. Set the
Maximum
Receive Size
equal to the size of the largest receive message packet for your application. This
parameter defines the Data Field size (M) for the input bytes.
The ToolLink Gateway can transmit serial message packets up to 68 bytes long. Set the
Maximum
Transmit Size
equal to the size of the largest transmit message packet for your application. This
parameter defines the Data Field size (N) for the output bytes.
Serial Interface
The
Serial Stream Object
attributes configure the serial channel’s baud rate, number of data bits and stop
bits, parity, and flow control. This configuration applies to both the serial transmitter and receiver. The
gateway has separate 128-byte serial transmit and receive FIFO buffers, allowing full duplex operation
when supported by the physical layer media.
The
Serial Stream Object
is also used to configure the message packet format
.
A message packet is
determined by one of three modes.
List
mode searches for
Pre-Delimiter
and
Post-Delimiter
byte strings
at the beginning and end of a message.
Length
mode captures a specific number of message bytes,
defined by
Packet Length
.
Timeout
mode uses an inter-byte delay (
Packet Timeout
) to signal the end of
a message. The following examples show the three
Serial Stream Object Delimiter
modes.
When the Receive Mode is set to List, the ToolLink Gateway uses start and stop delimiter strings to
identify the beginning and end of a message packet. The
Start Delimiter String
attribute defines the
beginning of a message, and the
Stop Delimiter String
attribute defines the end of a message.
The
Start Delimiter String
attribute format is [length][byte1][byte2][byte3][byte4]. The length byte is 0 to
4. The remaining byte(s) define the start of a message packet, which must be a unique byte string that is
not used elsewhere in the message packet. The ToolLink Gateway monitors received bytes for a match
to the Start Delimiter byte string. When a match is found, the start delimiter byte(s) and all subsequent
bytes are saved in the RX buffer, until a Stop Delimiter byte string is received. If the Start Delimiter String
is null (length = 0), the gateway starts saving the first received byte in the RX buffer.
The
Stop Delimiter String
attribute format is [length][byte1][byte2][byte3][byte4]. The length byte is 0 to
4. The remaining byte(s) define the end of a message packet, which must be a unique byte string that is
not used elsewhere in the message packet. Once a Start Delimiter String is received, the ToolLink
Gateway monitors the received bytes for a match to the Stop Delimiter byte string. When a match is
found, the gateway saves the stop delimiter bytes and the message packet is complete. If the Stop
Delimiter String is null (length = 0), then the gateway saves the start delimiter bytes and all subsequent
bytes until the
Maximum Receive Number
of bytes are received. This is a modified version of the
Length Mode, using a start message delimiter to signal the start of a new fixed length message packet.
When Receive Mode = TIMEOUT, the ToolLink Gateway waits for an inter-byte delay to signal the end of
a message packet. If the receiver is idle for more than 3.5 byte times (or 5 msec, whichever value is
greater), then all bytes received before the timeout are grouped into a single message packet.
STATUS
RXCTR
TXACK
LENGTH
1 byte
1 byte
1 byte
1 byte
M bytes
ToolLink DeviceNet Input Bytes
DATA FIELD
COMMAND
RXACK
TXCTR
LENGTH
1 byte
1 byte
1 byte
1 byte
N bytes
ToolLink DeviceNet Output Bytes
DATA FIELD
