LeCroy 8901A Operator's Manual page 8

Product Description
CAMAC Cycles
Clear, Initialize
and Inhibit
Block Transfer Mode
Service Requests (SRQ)
Serial Poll
Front Panel LED's
control information. The second and sequgiJtial_bytes_a£cept,
respectively, the CAMAC subaddress (A Code), station number
JJljJ Code) and three bytes of data for the"CAMAC write lines.
Once these registers have been loaded, the information will_be
XetaiiigdjintiLJ2iQdifieioi_poweru^^ the Gra^s-
tem controller must issue a Listen command in order to initiate
this loading procedure. The loading process can be terminated
after any number of bytes have been transferred by issuing a
Talk, Listen, Unlisten or IFC command.
A CAMAC cycle is executed every time the 8901A is com
manded to enter the Talk mode and a Service Request is not
pending. At the completion of the CAMAC cycle a DAV (Data
Valid) will be asserted. Every time a byte is accepted a new
byte is made available. When no more data is available, the
8901A asserts End of Identity (EOI).
The 8901A can be programmed to generate clear (C), initialize
(Z), or inhibit (I) signals on the dataway when a CAMAC cycle
is executed. The C and Z registers are cleared after the com
pletion of the next CAMAC cycle. The inhibit register will re
main set until it is programmed off.
The 8901A can be programmed to do a high speed block trans
fer of 8-, 16-, or 24-bit words from CAMAC modules with
read and increment capability. Following module addressing
and the appropriate control byte, a Talk command will start the
890 lA to read one, two, or three bytes of data and automati
cally initiate another CAMAC cycle. Approximately 2 psec
later (a programmable 40 tisec delay can be used for slow mod
ules) new data is available to be read. CAMAC cycles will con
tinue to be executed until a Q=0 (end of memory) condition
causes the 8901A to stop executing CAMAC cycles and exit the
transfer mode.
The 8901A will issue a Service Request when a LAM is set by a
CAMAC module, or when a CAMAC cycle is executed and a
Q=0 or X=0 response is detected.
When the 8901A is polled, it sends up to five status bytes to the
controller, terminating the Request after the controller reads the
status byte. For a LAM-generated Service Request, the LAM
must be cleared or disabled before the poll is taken, or else an
other service request will immediately be issued.
Talk: indicates when 890lA is a Talker.
Listen: indicates when 890 lA is a Listener.