HD64F2145 Datasheet, PDF (427/829 Pages) Renesas Technology Corp – Hitachi 16-Bit Single-Chip Microcomputer

15.9.6 Restrictions on Using DTC
When an external clock source is used as a synchronization clock, update TDR by the DTC or
RFU and wait for at least five ø 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 15.23).
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
t
LSB
D0
D1
D2
D3
D4
D5
D6
D7
Note:* When external clock is supplied, t must be more than four clock cycles.
Figure 15.23 Example of Transmission using DTC in Clocked Synchronous Mode
15.9.7 SCI Operations during Mode Transitions
Transmission: Before making a transition to module stop, software standby, 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 cancellation. If a 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 15.24 shows a sample flowchart for mode transition during transmission. Figures 15.25
and 15.26 show the pin states during transmission.
Before making a transition from the transmission mode using DTC transfer to module stop,
software standby, 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.
Rev. 2.0, 08/02, page 387 of 788