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7I76 24
REFERENCE INFORMATION
SSLBP
STOP ALL
A STOPALL command is issued to stop all channel communication. STOPALL
resets all channel variables and should always be issued by a driver when initializing the
SSLBP interface. A STOPALL followed by a START command can be used after a fault
condition to re-establish communication with the remote LBP devices. Device discovery
is only done once when START command is issued to a STOPed SSLBP. This means that
if cabling, devices, or device hardware modes are are changed, a STOPALL command
followed by a START command must be issued by the host to detect the changes. A
STOPALL command is 0x0800.
STOP INDIVIDUAL CHANNELS
In addition to stopping all channels, a individual stop command can be issued. A
individual stop command include a bitmask of the channels to stop in the least significant
8 bits of the command (the N bits), that is a stop channel 1 command would be 0x802. The
intended use of individual stop is per channel error recovery. It should not be used for
normal interface startup as it does not reset channel variables, that is a 0x8FF command
(stop all individual channels) is not equivalent to a 0X800 (STOPALL) command.
DOIT
In normal operation SSLBP is designed to send host data from the interface
registers to the remote device and request data from the remote device for presentation
in the interface registers to the host. This SSLBP function is designed for high speed real
time operation. Synchronization with the host is accomplished with the DOIT command.
When the host writes a DOIT command,, all outgoing process data from the host
is sent to the remote devices and incoming process data is requested. Completion of the
DOIT command is signaled by SSLBP clearing the COMMAND register. A DOIT command
is completed when al requested channel transfers have completed or timed out. After the
completion of a successful DOIT command, the incoming process data from the remote
can be read.
A DOIT command contains the DOIT bit and an 8 bit mask in the 8 LSBs that
selects the channels that will be requested to transfer data. A DOIT should not be
requested on an inactive channel, that is a channel that did not start. After DOIT
command completion the data register will contain a bit mask of channel status data. If any
bit is set in the data register, it indicates a problem with the transfer (all zeros indicates
no faults or errors).
The data register contents returned after a DOIT command can be used to minimize
host access cycles by avoiding the need to read the per channel status registers. If
detailed fault information is desired, the CS register can be read on any channel that
shows a failed transfer.