User guide

358 Advanced User Guide
13 Cables
Using the Remote Start/Stop cable
Remote start/stop is used to synchronize two or more
instruments. For example, you might connect an integrator and
the GC so that the [Start]/[Stop] buttons on either instrument
control both of them. You can synchronize a maximum of ten
instruments using Remote cables.
Connecting Agilent products
If connecting two Agilent products with Remote cables, the
sending and receiving circuits will be compatible—just plug in
both ends of the cable.
Connecting non-Agilent products
If connecting to a non- Agilent product, the following
paragraphs contain information you will need to ensure
compatibility.
APG Remote signal electrical specifications
The APG signals are a modified open collector type. The signal
levels are generally TTL levels (low voltage is logic zero, high
voltage is logic one) but the open circuit voltage will be between
2.5 and 3.7 Volts. The typical voltage is 3 Volts. A voltage over
2.2 volts will be interpreted as a high logic state while a voltage
below 0.4 volts will be interpreted as a low logic state. These
levels provide some margin over the specifications of the
devices used.
The pull- up resistance, connected to the open- circuit voltage, is
in the range of about 1K ohms to 1.5K ohms. For a logic- low
state, for a single device on the bus, the minimum current you
must be able to sink is 3.3 milliamps. Since devices are
connected in parallel, when you have multiple devices this
minimum current must be multiplied by the number of devices
attached on the bus. The maximum voltage for a low- input
state = 0.4V.
The bus is passively pulled high. Leakage current out of a port
must be less than 0.2 milliamps to keep the voltage from being
pulled lower than 2.2 volts. Higher leakage current may cause
the state to be interpreted as a low.
Over- voltage protection - APG Remote connections are clamped
by a zener diode to 5.6 Volts. Exceeding this voltage will damage
the circuit (main board).