https://priorart.ip.com/IPCOM/000099743

Micro Channel File Multiplexer The figure illustrates a MICRO CHANNEL*
file multi- plexer that permits a simultaneous connection of up to eight
direct-bus-attach hard files to a MICRO CHANNEL. In the past, an
implementation used was to hardwire a primary and a secondary address in
a file adapter, and all direct-bus-attach files have the same primary
and secondary addresses. With only two possible address assignments, one
is limited to a maximum of two files per computer system. The described
MICRO CHANNEL file multiplexer overcomes this two-file limitation and
demonstrates a simple way to facilitate the connection of up to eight
files at a time.

The MICRO CHANNEL is used on a motherboard in a test system which
connects to a PS/2* MICRO CHANNEL via an adapter card and extends to the
MICRO CHANNEL bus by several feet using cables. In addition, it provides
a multiplexing mechanism whereby up to eight hard files are attached to
the channel at one time. This test system brings the microprocessor bus
out of a system box and provides a simple means of attaching more adapters.

MICRO CHANNEL-compatible files transfer information to and from the
channel in two modes. One mode is as an I/O device for commands and
status, and the other mode is as a DMA-Slave device for data. In both
modes, the file accepts or presents information only on bus cycles when
its I/O address, card select signal, or Arbitration ID are valid and the
bus signal IO is low.

The circuit shown in the figure exploits ...