QEI 7BI1, Manual

Page: 8 / 13

Manual 909 7BI1Bus Interface 7BI1
Bus Interface
Copyright © 2018 QEI Theory of Operation

11
3 Theory of Operation
The key to understanding the 7BI1 is to understand the address strapping options. Since the
6CPP2 can only address eight (8) 3150 cards, there must be a means of selecting these
eight (8) from the sixteen (16) possible addresses which the 6CP2 can normally handle. This
is done via the X1 through X8 platforms.
The 6CP2 selects other 3150 cards within the card frame via a four-by-four address matrix
(XO-X3, YO-Y3). The 7BI1 must, therefore, simulate these signals.
The address signals coming from the J4 connector of the 6CPP2 consist of eight (8)
individual address signals (XYO-XY7) and a group address signal (4000-40FF). Platforms
X1 through X8 convert these signals into the form used by the 6CP2. That is, every one of
the eight (8) individual address signals can generate two signals in the four-by-four address
matrix (one X and one Y).
Since many of these signals can overlap, the strapping is done with diodes which essentially
OR's the addresses together. That is, up to four (4) different address signals from the 6CPP2
could use the same X address (X2 for instance). Each platform generates one of the address
signals in the four-by-four address matrix. Table 3-1 defines the platforms and their
corresponding matrix signal.
TABLE 3-1. Platform/Matrix Signal
PLATFORM 4 X 4 SIGNAL
X1 X0
X2 X1
X3 X2
X4 X3
X5 Y0
X6 Y1
X7 Y2
X8 Y3
The eight (8) address signals from the 6CPP2 and what they normally correspond to, are
shown in Table 3-2.
TABLE 3-2. Signals & What They Correspond To
Platform PIN Address Function Position
XY0 6TM1 1
XY1 6CM 2
XY2 6AD 3
XY3 6SI (1st) 4
XY4 6SI (2nd) 5
XY5 6SI (3rd) 6
XY6 6SP 7
XY7 6FD 8
Each address signal connects to the same position on each of the eight (8) platforms. That is,
XYO connects to position 1 (pin 1) on all of the platforms. Similarly, XY1 connects to position
2 (pin 2) on all of the platforms. This is also shown in Table 3-2. This gives any of the eight
address signals from the 6CPP2 the capability of selecting any two of the four-by-four
address matrix signals (one X and one Y). The two are selected by placing a diode in the
positions desired. Table 3-3 shows the relationship between the positions and the slot
numbers of the 3150 Remote card frame.