Mode 7 Power Up. - Brainboxes PS-307 User Manual

PSI BOX Reference
PS/2 IEEE controller.
The PSI BOX acts as the IEEE controller and is the source
of all IEEE commands. It controls the flow of data on the IEEE
bus by addressing and un addressing devices to talk or listen. Up
to 14 IEEE devices may be accessed when in this mode.
A sophisticated command language is used to control the
IEEE bus via the PSI BOX. It is similar in concept to the
HAYES modem control language, and the commands and syntax
are based on those used in the our Professional 488 Device
Driver for our range IBM PC and PS/2 compatible IEEE
interface. The character sequence that invokes the IEEE
command language is <CR> BUS
Characters sent to the PSI BOX that do not start with the <CR>
BUS sequence are treated as data to be sent direct to the current
IEEE device, the data is thus passed straight through from the
RS232 port to the IEEE bus.
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Mode 7 Power Up.

The basis of the Mode 7 IEEE handler is an intelligent
command handler. This is a piece of software resident on the
PSI BOX rom. It is called into operation automatically whenever
the PSI BOX is powered up or reset when DIP switches are set
to Mode 7 as shown in the PSI BOX manual page 7 Figure 4.
Once the PSI BOX has been powered on in Mode 7 you
can access the IEEE bus in two ways. By default data sent to
the PSI BOX from the RS232 computer is passed though to the
current IEEE device. Alternatively the data sent to the PSI BOX
is interpreted as a Mode 7 BUS command.
When the PSI BOX is switched on in MODE 7 it sets up
and maintains a list of parameters, the IEEE control status string.
These parameters describe the current IEEE address, secondary
address, state of ATN, SRQ and REN lines, input and output
Page 70
Mode 7 Overview
Chapter 7