Allen-Bradley 1771-ASB

The Allen-Bradley 1771-ASB Remote I/O Adapter Module physically resides in a Universal I/O Chassis, and acts as a slave in an Allen Bradley subnet in an EPICS control system. The 1771-ASB Remote I/O Adapters are linked via subnet connection to other Remote I/O Adapters in Allen Bradley 1771 Series I/O Chassis, Allen-Bradley RediPANEL Pushbutton Modules, and back to a VMEbus I/O scanner. They correspond to the ADAPTER number when configuring an Allen-Bradley subnet. An Allen-Bradley / EPICS subnet allows for up to 8 adapters to be located on one Allen-Bradley subnet link.

The remote I/O adapter module serves as an interface between remote I/O modules and programmable controllers. The remote I/O adapter:
- transmits data up to 10,000 cable-feet (at 57.6K baud)
- provides faster backplane scanning and data transmission up 2500
cable-feet at 230.4K baud
- receives/sends data from/to the I/O scanner in serial form
- reads/writes data from/to the input modules in parallel form
- reads/writes data from/to the output modules in parallel form
- supports any mix of I/O (4, 6, 8, 16 or 32 points)
- supports three methods of I/O addressing; 1/2-slot, 1-slot and 2-slot
- checks I/O configuration on power-up to verify I/O module placement
- scans all slots in the chassis, or all but the last four slots, allowing improved scan time and I/O image space savings. Slot power supplies can be used in the last quarter of the rack without using I/O space.
- can emulate series B adapters, providing system response similar to the 1771-ASB series B. This allows use of 1771-S4A and -S4B scanners which require slower response for proper operation.


The remote I/O adapter module is one of many hardware components that make up a programmable controller system. There are three steps involved in the configuration of a 1771-ASB Remote I/O Adapter Module, the first involves the setting of the Module Configuration Plug or Plugs, the second involves the setting of the Module Switches, and the third involves the setting of the Universal I/O Chassis backplane switches located on the left hand, lower side of the backplane as you look into the chassis. Note that there are two styles of Remote I/O Adapter, they are easily discerned by looking at SW 2. In the older style module SW 2 is a 4 position DIP switch, in the newer style, SW 2 is a 6 position DIP switch.