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4.4 Writing Data to the CAMAC Command Stacks and to the NAF Generator
The Out Packets targeting the two CAMAC Stacks and the CAMAC NAF Generator have
identical structure, differing only in the Target Address and in length:
1. Target Address
2. Number of words in the stack
3-N. Sequence of stack words
The CAMAC Data Stack (Address=2) is 768 words deep and is intended for storing
information on the sequence of the CAMAC commands to be performed when an event
readout is initiated. The CAMAC Scaler Stack (Address=3) is 256 words deep and is
intended for storing information on the sequence of the scaler readout commands, when a
periodic readout of scalers is desired. The CAMAC NAF Generator (Address 8) is an internal
module that interprets the information found either in the CAMAC Stacks (when CC-USB is
in data acquiring mode) or in the Out Packet received from the USB port (when CC-USB is
in interactive mode).
4.5 Structure of the CAMAC Stack
The CAMAC stack consists of a sequence of properly encoded simple (one line for CAMAC
"Read" commands and 3 lines for CAMAC "Write" commands) or complex (multi-line)
CAMAC commands.
Simple commands specify only the desired N, A, and F to be issued by CC-USB and,
additionally, whether the data is 24-bits (Long Mode) or 16-bits long For the CAMAC
"Write" commands, additional two lines specify the data to be written.
The data word for a simple command has the following structure:
15
0
Long Mode
This data word can thus be calculated as
SimpleCommand = F+32*A+512*N+16384*LongMode
Note, that the CAMAC "Read" commands have both bits 3 and 4 (the most significant bits)
of F set, while the "Write" commands have only bit 4 set. Control commands have bit 3 set.
Complex commands are possible only for "Read" operations. The first word of a complex
commands is similar to a simple command, except that it has bit 15 (continuation bit) set, i.e.
WIENER, Plein & Baus GmbH
14
9-13
N
2, 3, or 8, for CDS, CSS, and CNAF, respectively
where N=Number of words in stack + 2
5-8
A
18
0-4
F
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