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disregarded in earlier firmware versions (<6.1). The stack data are continued by 2 lines with
16-bit words for each 32 bit instruction.
The VME Command Generator (VCG) is an internal module that interprets the information
found either in the VME Stacks (when VM-USB is in data acquisition mode) or in the Out
Packet received from the USB port (when VM-USB is in interactive mode / EASY-VME
mode). In the latter case the VCG performs a VME command stack, which can be longer
than the stack memory itself in order to perform more complex functions. The content of the
second line depends on whether the stack data are to be stored in the stack memory or
whether the stack is to be executed interactively. In the former case, it contains the starting
address of the stack within the stack memory space and in the latter case it represents the
high 16 bits of the number of lines in the long VCG stacks.
Please see the example and comments about stack generation at the end of chapter 4.5.
1. Target Address:
5
VCS ID Bits1-2
2. Stack size: Number of subsequent words (low word of Number for VCG)
3. Stack starting address (high word of Number for VCG)
4. Stack word 1
5. Stack word 2
...
N*2. Last stack word ( N=Number of 32-bit words in stack + 2)
4.5 Structure of the VME Stack
The VME stack consists of a sequence VME commands encoded in 32-bit words. Every
command is encoded in two or more words, with the first one always specifying the VME
address modifier along with a number of options (Mode Word)). With the exception of multi-
block transfer, the second word specifies the VME address (Address Word).
The first Mode Word stores the 6-bit VME address modifier, along with other data defining
the write/read mode and the format of the VME data, and some additional options:
15
14
*
DLY
31-24
23-22
BLT
Where the individual bits have the following meaning:
WIENER, Plein & Baus GmbH
4
3
VCG Bit
13
12
11
MRK
SLF MB
21-20
19
NT
*
HM
8 VCS (ID 0-7) and VCG
2
Write Bit
VCS Bit
10
9
8
NA
*
NW
18
17
ND
HD
26
1
0
VCS ID Bit 0
7-6
5-0
DS
AM
16
BE
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