558
Equation 2:
When D = 0.5 and F = 0:
M
=
(0.5 – 1/(2
×
16))
×
100
%
=
46.875
%
This is a theoretical value. A reasonable margin to allow in system designs is 20% to 30%.
7. Note on Use of Modem Signals: The following bug may occur when modem signals are used
by the SCIF (serial communication interface with FIFO) (i.e. when the MCE bit in SCFCR is set
to 1).
•
Conditions
When, in transmission, the CTS signal goes high when the last byte of data in the FIFO has
been transmitted.
“When the last byte of data in the FIFO has been transmitted” means the state in which there is
data in SCTSR only (and no data in SCFTDR), and that data, including the start bit, has been
output to TxD. It does not cover the case where the next data is written to SCFTDR before
transmission of the last data is started.
•
Problem
Transmission may halt midway through a frame when the entire frame should be transmitted
(from start bit to stop bit). In this case, a high level is output from TxD.
•
Preventive Measures
This bug can be avoided by taking the following measures.
Do not perform hard flow control with the CTS signal.
Use an IRQ signal instead of the CTS signal, and control starting and stopping of
transmission by means of interrupt handling.
Perform transmission/reception with dummy data as the last data (in systems where this is
permissible).
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Страница 292: ...273 T1 CKIO A25 to A0 CSn RD WR RD D31 to D0 WEn D31 to D0 BS T2 Read Write Figure 10 6 Basic Timing of Basic Interface ...
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