Hameg HO88, Manual

Page: 14 / 48

Änderungen vorbehalten / Subject to change without notice
14
and IEEE-488 of the Institute of Electrical and Electronic Engineers - contain binding
stipulations for assignment of the lines to the device connectors (Figure 1). Either ribbon
cables or round cables with single or double shielding and twisted conductors are used.
Up to a total of 16 devices - including instruments, controllers, and peripherals - can be
connected to the IEEE-488 bus at any one time. This restriction to 16 devices is a
consequence of the limited driving capability of the bus. It is defined at
≤
48 mA. The
current consumption of each device driver is
≤
3 mA (15 d 1 controller with 3
mA each = 48 mA). The IEEE-488 bus uses negative logic with standard TTL logic
levels between 0V and 5V. Logic 0 is a -TTL high level (
≥
2.0V), and logic 1 is a TTL low
level
≤
0.8V).
Figure 1: IEEE-488 bus connector configuration
Attention: The 25-pin connector specified by the IEC-625 standard is easy to
confuse with the 25-pin connector normally used for RS-232C-serial interfaces.
Use of the wrong connector can result in serious damage to the interface
electronics!
Figure 2: Shielded IEEE-488 round multiconductor
No other interface for communications with peripheral devices is so precisely defined
as the IEEE488 bus, from the bus protocol all the way to connector pin assignments.
The only limitations for connection of devices are that one device should be added for
every two meters of cable (although they need not be equally spaced along the length
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