A Multiblock Capable Slave may be Configured as a Primary Link, a Middle Link or an End Link and then participate in Multiblock operations. It may also be configured to not be active in a Multiblock Group.
A Multiblock Capable Slave shall be capable of operating in
Multiblock Mode at any position in a Multiblock Group. Its
configuration shall be defined by the value of
CSR#xxyy,zz
as
shown in Table 31.
RB or Reset (CSR#0
) shall set these bits to 00. RB or
Clear Error (CSR#0
) shall have no effect on the state of
these bits.
Multiblock Capable Slaves may have any other normal attributes of FASTBUS Slaves.
A Multiblock Capable Slave shall at all times respond to any
normal FASTBUS operations for which it is designed.
Data in a Multiblock Capable Slave is located in (DSR) #1 which
is FIFO-like in operation, i.e., many words of data may be read
or written in sequence without changing the NTA. During normal
operations an end-of-buffer is indicated by an SS=2 response.
Data accessible in Multiblock Mode shall be accessible through
DSR#1 which shall act as a FIFO-like device.
In the Primary Link, DSR#2 is a FIFO-like virtual location through which DSR#1 of each of the Slaves in the Multiblock Group is be accessed in turn.
A Primary Link shall contain a virtual DSR#2 which emulates a
large buffer containing all the DSR#1 buffers of Slaves in its
associated Multiblock Group.
An attempt to access DSR#2 in a Multiblock Capable Slave that is not configured as a Primary Link should result in an SS=6 error.
A Multiblock activity indicator provides as a simple visual indication of response in Multiblock Mode.
Immediately below the Module Activity Indicator(s) a
Multiblock Capable Slave shall have a second yellow LED which
shall be lit by a monostable
whenever the Module is
transferring data in Multiblock Mode.