TC1796
Peripheral Units (Vol. 2 of 2)
Micro Link Interface (MLI)
User’s Manual
23-37
V2.0, 2007-07
MLI, V2.0
normally. If Automatic Data Mode is disabled, no blocking mechanism has been
implemented. The Remote Controller software has to take care to read the
received data.
23.2.1.4 Answer Frame
Please note that only one Answer Frame can be handled by the system at a time (no
Read Frame request while any TRSTATR.RPx is set). Make sure that not more than one
Read Frame is pending at a time. If a Read Frame is not answered by an Answer Frame
during a certain time interval, a time-out criterion should be handled in software. The
Remote Controller has to take care that no Answer Frame is delivered after the time-out
criterion has been detected (e.g. by a software-triggered Command Frame). Do not start
a new Read Frame while waiting for an Answer Frame if the time-out criterion has not
yet been detected and the Answer Frame has not yet been received. The length of the
time-out interval depends on the application and has to be defined accordingly on a case
by case base (e.g. the transfer rates between MLI modules, bus architecture, etc. have
to be considered). In the case a time-out has been detected, the Local Controller
software has to clear the TRSTATR.RPx bit by writing 1 to SCR.CDVx and can start a
new Read Frame.
Remote Controller (Receiving the read request)
The Answer Frame is the only frame sent from the Remote Controller back to the Local
Controller. The transmitter registers of the Remote Controller are used to generate the
Answer Frame.
Every time the transmitter data read answer register TDRAR is written in the Remote
Controller, the transmission of an Answer Frame is started and the following actions are
triggered.
•
Status flag TRSTATR.AV is set to trigger the transmission of an Answer Frame.
The following parameter is transmitted in the data field of the Answer Frame:
•
Read data: stored in TDRAR.DATA; data width is determined by TRSTATR.DW.
•
Status flag TRSTATR.AV is cleared after the Answer Frame has been finished and
correctly acknowledged by the MLI receiver of the Local Controller.
An Answer Frame should be sent through the pipe that has received a read request but
there must be only one MLI Transfer Window read access pending on any side of a MLI
connection at any time, because the answer mechanism does not contain buffers for
multiple Answer Frames.
Local Controller (Transmitting the read request)
If an Answer Frame has been received correctly and acknowledged, the following
actions are executed in the MLI receiver of the Local Controller: