LeCroy 8901A Operator's Manual page 30

Additional Information
Function Codes
The function to be performed at the specified subaddress in the
selected module or modules is defined by the signals on the five
F bus lines (F16, F8, F4, F2, Fl). These signals are decided
in the module to select one of up to 32 functions, numbered in
decimal from F(0) to F(31). To see to which functions a par
ticular LeCroy instrument reacts, see its manual.
CAMAC Data
A common parallel highway is used for all data transfers. All
information carried by the parallel highway is conveniently de
scribed as data, although it may be information concerned with
status or control features in modules. Up to 24 bits may be
transferred in parallel between the controller and the selected
module. Independent lines (Read and Write) are provided for
the two directions of transfer.
The Write Lines
The crate controller generates data signals on the 24 parallel W
bus lines (W1-W24) at the beginning of any Write operation.
The Read Lines
Data signals are set up on the 24 parallel R bus lines (R1-R24)
by the instrumentation module as soon as a Read command is
recognized. An interface such as the 8901A strobes data from
the R bus lines into its own internal registers, whereafter the
data is appropriately formatted for GPIB compatible transfers.
Status Information
CAMAC status information is conveyed by signals on the LAM,
Busy (B), Response (Q) and Command Accepted (X) lines.
This status information is similar to the GPIB service request.
Look-at-Me (LAM) This, like the N Line, is an individual connection from each
station to a separate pin at the control station. When there is
no Dataway operation in progress (no B present) any plug-in
unit may generate a signal on its L line to indicate that it re
quires attention, such as is the case when a waveform recorder
has finished a conversion sequence. A LAM request can be
reset by Clear LAM, Initialize, or by the performance of the
specific action which generated the request.
Q Response
Command
Accepted
The Q busline is used during a Dataway operation to transmit a
signal indicating the status of a selected feature of the module,
such as whether or not data being read is valid.
Whenever a module is addressed during a command operation it
must generate an X=1 on the Command Accepted busline (X) if
it recognizes the command as one that it is equipped to per
form.
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