Restrictions On Using Dtc; Sci Operations During Mode Transitions; Figure 14.33 Sample Transmission Using Dtc In Clocked Synchronous Mode - Renesas H8S Series Hardware Manual

14.9.5

Restrictions on Using DTC

When the external clock source is used as a synchronization clock, update TDR by the DTC and
wait for at least five φ clock cycles before allowing the transmit clock to be input. If the transmit
clock is input within four clock cycles after TDR modification, the SCI may malfunction (figure
14.33).
When using the DTC to read RDR, be sure to set the receive end interrupt source (RXI) as a DTC
activation source.
SCK
TDRE
Serial data
Note: When external clock is supplied, t must be more than four clock cycles.

Figure 14.33 Sample Transmission using DTC in Clocked Synchronous Mode

14.9.6

SCI Operations during Mode Transitions

Transmission: Before making the transition to module stop, software standby, watch, sub-active,
or sub-sleep mode, stop all transmit operations (TE = TIE = TEIE = 0). TSR, TDR, and SSR are
reset. The states of the output pins during each mode depend on the port settings, and the pins
output a high-level signal after mode is cancelled and then the TE is set to 1 again. If the transition
is made during data transmission, the data being transmitted will be undefined.
To transmit data in the same transmission mode after mode cancellation, set TE to 1, read SSR,
write to TDR, clear TDRE in this order, and then start transmission. To transmit data in a different
transmission mode, initialize the SCI first.
Figure 14.34 shows a sample flowchart for mode transition during transmission. Figures 14.35 and
14.36 show the pin states during transmission.
Before making the transition from the transmission mode using DTC transfer to module stop,
software standby, watch, sub-active, or sub-sleep mode, stop all transmit operations (TE = TIE =
TEIE = 0). Setting TE and TIE to 1 after mode cancellation generates a TXI interrupt request to
start transmission using the DTC.
Section 14 Serial Communication Interface (SCI)
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Rev. 6.00 Mar 15, 2006 page 379 of 570
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