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SECTION 5 B R E A D B O A R D APPLICATIONS
5.1 I N T R O D U C T I O N S
5.1.1
T h e
7064-20 has many features and great flexibility. This information describes
some o f the features, and give examples o f how typical circuits can be
implemented.
5.2 R E G I S T E R S
5.2.1
A
l
l
VXlbus devices have a set of registers that appear in the A16 address space.
Each device is given 64 bytes of A16 address space for its registers. Register-
based devices have four 16-bit registers that are normally implemented. Three of
these registers are read registers. They are ID Register, Device Type Register, and
Status Register. There is one Write Register - the Control Register. There is an
optional Read/Write Register called the Offset Register. All of the rest of the A16
address space beyond the lower four registers is devoted to Device dependent
registers. These registers can be used for any desired purpose.
Status Register
There are 12 bits in the Status register that are called device dependent. This
means they can be used by the instrument designer for whatever purpose is
desired. The register-based breadboard implements four of these device dependent
bits. These bits are controlled by the levels at E18, E19, E20 and E21. The
designer can also control the PASSED and READY bits in the Status register by
controlling the levels of E16 and E17. The MODID bit is automatically controlled
by the MODID bit on the backplane. The A24/A32 bit is automatically controlled
by the A24/A32 enable bit in the control register. I f the device designer wants to
implement the additional device dependent bits (6 through 13), that is easily
accomplished with one additional IC. Here is an example circuit that shows how
it can be done:
9176
141
9177
142
91T8
143
9179
144
5 1 710
241
piT1 1
2A2
1T12
2A3
' ' . 17 13
2A4
C 1 0
015
(STATENA.)
C
7 2 , H C T : 4
VXI Status Register Expansion
REGISTER-BASED
19
9 0 6
(PIIA71
1Y1
6
9 D
7
P11491
1Y2
(P1,A9)
-D8
153
='09
1-4
10
P. 4 1
2Y1
1 14 )
6
252
P11413)
iD 2
:Y3
IP11 4 1
- 0 1 3
254
5-1
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