Problem in the Interface between the 2988 and the FEPs

EMAS sends messages to the FEPs in the form:-
   <write control> <stream id> <max transfer length> <limit>
followed by:-
   <write> <max bytes of data> <limit>
where <write control> <write> and <limit> are all 'control' characters,
ie the ninth bit is set to distinguish them from data.

The case of <stream id> = -2 is special in that bytes of data are
sent from the 2988 in multiples of 24 bytes up to a maximum of 192 bytes.
In the case that causes the current problems either the 4 byte header
packet (<stream id> <transfer size>) is not followed by a <limit> or
the <stream id> = -2 data bytes are not terminated by a <limit>, the FEP
will then read up to 200 bytes of data before detecting an error.

In all other cases a missing <limit> will not be noticed by the FEP as
the FEP itself decides how many data bytes to accept.

                                                    Brian Gilmore
                                                    25th Nov 1982