ToolLink User Manual
MKS Instruments, Inc.
Page 26 of 30
I/O Response
Status
Rx Counter
TX
ACKNOWLEDGE
Length Data
TX Handshake Enable – Attribute 11
By default (TX Handshaking disabled,) the data in the I/O command is transmitted each time the I/O
command is written with a non-zero value for Length. If the user polls the CDN466 for newly received
serial data, the Length field must be set to zero if no data is to be transmitted.
In this case, the TX Counter performs no function and should remain at zero.
With TX Handshaking enabled, transmission of serial data is triggered from the TX Counter rather than
from the Length field. The data in the I/O response is transmitted to the serial connection when the value
of TX Counter is incremented from its previous state.
The value of TX Acknowledge will increment automatically after data from the I/O command has finished
transmitting to the serial connection. If the user waits for TX Acknowledge to increment before triggering
the transmission of new data, the user should not be able to overflow the transmit buffer.
Figure 2: TX Handshaking
I/O Commad
Command
RX
ACKNOWLEDGE
TX Counter
Length
Data
I/O Response
Status
Rx Counter
TX
ACKNOWLEDGE
Length Data
Maximum Rx Size – Attribute 19
Value = 0 to 64 (default 16)
Maximum Rx Size sets the length of the data field in the I/O response. It should be set greater or equal to
the value of the largest message to be received from the serial connection. The produce size of the I/O
connection will be configured to 4 + Maximum TX Size (4 control bytes + Maximum Rx Size data bytes.)
Maximum TX Size – Attribute 20
Value = 0 to 64 (default 16)
Maximum TX Size sets the length of the data field in the I/O command. It should be set greater or equal
to the value of the largest message to be transmitted to the serial connection. The consume size of the
I/O connection will be configured to Maximum TX Size + 4 (4 control bytes + Maximum TX Size data
bytes).
Rx Handshaking Disabled:
Increments automatically with new serial data if Rx Handshaking enabled.
Rx Handshaking Enabled:
Holds value and serial data until user performs acknowledgement.
TX Handshaking Disabled:
No function
User sets to zero.
TX Handshaking Enabled:
User increments to transmit
new data.
Rx Handshaking Disabled/Enabled:
Increments
automatically each time data written in the I/O command
finishes transmitting to the serial connection.
TX Handshaking Disabled:
Triggers Serial transmission
when set to non-zero value.
TX Handshaking Enabled:
Does not trigger transmission
of data.
