Chapter 4
Register Descriptions
© National Instruments Corporation
4-41
VME-MXI-2 User Manual
VMEbus Interrupt Acknowledge Register 4 (VIAR4)
VMEbus A16 Offset:
38 (hex)
Attributes:
Read Only
32, 16, 8-bit accessible
31
30
29
28
27
26
25
24
I4[31]
I4[30]
I4[29]
I4[28]
I4[27]
I4[26]
I4[25]
I4[24]
23
22
21
20
19
18
17
16
I4[23]
I4[22]
I4[21]
I4[20]
I4[19]
I4[18]
I4[17]
I4[16]
15
14
13
12
11
10
9
8
I4[15]
I4[14]
I4[13]
I4[12]
I4[11]
I4[10]
I4[9]
I4[8]
7
6
5
4
3
2
1
0
I4[7]
I4[6]
I4[5]
I4[4]
I4[3]
I4[2]
I4[1]
I4[0]
This register generates a VMEbus Interrupt Acknowledge (IACK) cycle for interrupt
level 4 when read from the MXIbus and returns the Status ID received from the
interrupter. It can generate 32-bit, 16-bit, or 8-bit IACK cycles. Generating an 8-bit
IACK cycle requires reading offset 39 (hex). When read from the VMEbus, this register
does not generate an IACK cycle and returns FFFFFFFF (hex).
Bit
Mnemonic
Description
31-0
I4[31:0]
Level 4 Interrupter Status ID
These bits return the Status ID received during
the IACK cycle.
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