
Section 10 Serial Communication Interface
Rev. 6.00 Sep 12, 2006 page 340 of 526
REJ09B0326-0600
7. Relation between RDR reads and bit RDRF
In a receive operation, SCI3 continually checks the RDRF flag. If bit RDRF is cleared to 0
when reception of one frame ends, normal data reception is completed. If bit RDRF is set to 1,
this indicates that an overrun error has occurred.
When the contents of RDR are read, bit RDRF is cleared to 0 automatically. Therefore, if bit
RDR is read more than once, the second and subsequent read operations will be performed
while bit RDRF is cleared to 0. Note that, when an RDR read is performed while bit RDRF is
cleared to 0, if the read operation coincides with completion of reception of a frame, the next
frame of data may be read. This is illustrated in figure 10.27.
Communication
line
RDRF
RDR
Frame 1
Frame 2
Frame 3
Data 1
Data 1
RDR read
RDR read
Data 1 is read at point
(A)
Data 2
Data 3
Data 3
(A)
Data 2 is read at point
(B)
(B)
Figure 10.27 Relation between RDR Read Timing and Data
In this case, only a single RDR read operation (not two or more) should be performed after
first checking that bit RDRF is set to 1. If two or more reads are performed, the data read the
first time should be transferred to RAM, etc., and the RAM contents used. Also, ensure that
there is sufficient margin in an RDR read operation before reception of the next frame is
completed. To be precise in terms of timing, the RDR read should be completed before bit 7 is
transferred in synchronous mode, or before the STOP bit is transferred in asynchronous mode.
Summary of Contents for F-ZTAT H8/3642A Series
Page 6: ...Rev 6 00 Sep 12 2006 page iv of xx ...
Page 8: ...Rev 6 00 Sep 12 2006 page vi of xx ...
Page 22: ...Rev 6 00 Sep 12 2006 page xx of xx ...
Page 124: ...Section 5 Power Down Modes Rev 6 00 Sep 12 2006 page 102 of 526 REJ09B0326 0600 ...
Page 188: ...Section 6 ROM Rev 6 00 Sep 12 2006 page 166 of 526 REJ09B0326 0600 ...
Page 190: ...Section 7 RAM Rev 6 00 Sep 12 2006 page 168 of 526 REJ09B0326 0600 ...
Page 298: ...Section 9 Timers Rev 6 00 Sep 12 2006 page 276 of 526 REJ09B0326 0600 ...
Page 378: ...Section 12 A D Converter Rev 6 00 Sep 12 2006 page 356 of 526 REJ09B0326 0600 ...
Page 446: ...Section 13 Electrical Characteristics Rev 6 00 Sep 12 2006 page 424 of 526 REJ09B0326 0600 ...