$OPTION
This word is to be filled by the master. Each bit of this word can be used to enable a software option in the SSP. The definition of the bits are SSP_dependent. If the option word is equal to zero, no options are enabled. The option word must be filled by the master before the command INIT is given, and must remain unchanged for the other commands. If $OPTION is changed, the initialization must be repeated.
Failure to ensure that $OPTION remains unchanged throughout the run may cause routines to fail, since $OPTION bits may affect what slave modules are to be initialized.
A FORTRAN INCLUDE file (in 787SSP:) should be provided by the SSP programmer that gives the assignments of the bits in $OPTION. For example, the file DC_OPTION_BITS.INC contains the bit assignments (and bit-mask) for the drift chamber SSP.
This word is used to set a limit on the total length of the data obtained by variable length reads during one event. Any extra words will be discarded, and the counter $OVERFLOW (see $OVERFLOW) should be incremented. An error bank may be produced.
What this maximum number actually refers to is SSP_dependent. For example, if a fixed number of words is read every event, $MAX_VAR will be ignored. If part of the event is a variable length read, and part fixed, $MAX_VAR will refer to the maximum length of the variable part only.
This word may be used to estimate the maximum event size expected (needed for checking for free space in the data buffer). It may be convenient (for debugging) to load this location with a default value (this can be done in BNL787_RES.MAR, see TEMPORARY_VERSION_OF_BNL787_RES.
This word is used to set a minimum value on the length of the data obtained by variable length reads during one event. If the minumum is not reached, the counter $UNDERFLOW (see $UNDERFLOW) will be incremented. The event should not be discarded, but an error bank may be produced.
What this minimum number actually refers to is SSP_dependent. For example, if a fixed number of words is read every event, $MIN_VAR will be ignored. If part of the event is a variable length read, and part fixed, $MIN_VAR will refer to the minimum length of the variable part only.
It may be convenient (for debugging) to load this location with a default value (see TEMPORARY_VERSION_OF_BNL787_RES).
This word is used to set a limit on the number of datawords obtained from any one module during one event. The data from the module must be of variable length. The exact use of $MOD_MAX is SSP_dependent; it is ignored for fixed length reads.
If $MOD_MAX is exceeded, an error bank may be added to the event. Counting of events where $MOD_MAX is exceeded, is SSP_dependent.
It may be convenient (for debugging) to load this location with a default value (see TEMPORARY_VERSION_OF_BNL787_RES).
If a slave module is busy when a master attempts to read the data, an SS=1 (busy) response is received. The master is expected to retry sometime later with every expectation of success. $RETRY_MAX contains the maximum number of retries on receipt of this condition before giving up, and continuing with the next module. The time delay between retries is SSP_dependent - for example a loop may be used to produce a time delay.
An error bank may be added to the event if the number of retries is exceeded. Counting of events where this occurs is SSP_dependent. It may be convenient (for debugging) to load this location with a default value (see TEMPORARY_VERSION_OF_BNL787_RES).
Converted from .HLP to .HTML by HLPTOHTML.