Channel.connectrule - Keithley 708B Reference Manual

Section 7: Command reference

channel.connectrule

This attribute controls the connection rule for closing and opening channels in the instrument.
Type TSP-Link accessible
Attribute (RW) Yes
Usage
rule = channel.connectrule
channel.connectrule = rule
rule
Details
The connection rule describes the order in which switch channels are opened and closed when using
channel.exclusiveclose(), channel.exclusiveslotclose(), and scanning commands like
scan.execute() and scan.background(). These commands may both open and close switch channels in
a single command. The connection rule dictates the algorithm used by the instrument to order the opening and
closing of switches.
The connection rule affects the operating time of these commands. These commands do not allow the instrument
to continue execution until the settle time of the relays has expired.
When the connection rule is set to channel.BREAK_BEFORE_MAKE, the instrument ensures that all switch
channels open before any switch channels close. When switch channels are both opened and closed, this
command executes not less than the addition of both the open and close settle times of the indicated switch
channels.
When the connection rule is set to channel.MAKE_BEFORE_BREAK, the instrument ensures that all switch
channels close before any switch channels open. This behavior should be applied with caution because it will
connect two test devices together for the duration of the switch close settle time. When switch channels are both
opened and closed, the command executes not less than the addition of both the open and close settle times of
the indicated switch channels.
With no connection rule (set to channel.OFF), the instrument attempts to simultaneously open and close switch
channels in order to minimize the command execution time. This results in faster performance at the expense of
guaranteed switch position. During the operation, multiple switch channels may simultaneously be in the close
position. Make sure your device under test can withstand this possible condition. When switch channels are both
opened and closed, the command executes not less than the greater of either the open or close settle times of
the indicated switch channels.
You cannot guarantee the sequence of open and closure operations when the channel connect rule
set to OFF. It is highly recommended that you implement cold switching when the channel connect
rule is set to OFF.
In general, the settling time of single commands that open and close switch channels depends on several
factors, such as card type and channel numbers. However, the opening and closing of two sequential channels
including no others can be guaranteed as follows:
7-20
Models 707B and 708B Switching Matrix Reference Manual
Affected by
System reset
•
channel.BREAK_BEFORE_MAKE or 1: Break-before-make (BBM)
connections for relays in the instrument
•
channel.MAKE_BEFORE_BREAK or 2: Make-before-break (MBB)
connections for relays in the instrument
•
channel.OFF or 0: Does not guarantee a connection rule. The instrument
closes relays as efficiently as possible to improve speed performance without
applying a rule
NOTE
Where saved Default value
Create channel.BREAK_BEFORE_MAKE
configuration script
707B-901-01 Rev. A / August 2010