Hitachi H8S/2338 Series Hardware Manual page 459

Restrictions on Use of DMAC or DTC
• When an external clock source is used as the serial clock, the transmit clock should not be
input until at least 5 ø clock cycles after TDR is updated by the DMAC or DTC. Misoperation
may occur if the transmit clock is input within 4 ø clocks after TDR is updated. (Figure 11-22)
• When RDR is read by the DMAC or DTC, be sure to set the activation source to the relevant
SCI receive-data-full interrupt (RXI).
SCK
TDRE
Serial data
Note: When operating on an external clock, set t > 4 clocks.
Figure 11-22 Example of Synchronous Transmission Using DTC
Operation in Case of Mode Transition
• Transmission
Operation should be stopped (by clearing TE, TIE, and TEIE to 0) before making a module
stop mode or software standby mode transition. TSR, TDR, and SSR are reset. The output pin
states in module stop mode or software standby mode depend on the port settings, and
becomes high-level output after the relevant mode is cleared. If a transition is made during
transmission, the data being transmitted will be undefined. When transmitting without
changing the transmit mode after the relevant mode is cleared, transmission can be started by
setting TE to 1 again, and performing the following sequence: SSR read → TDR write →
TDRE clearance. To transmit with a different transmit mode after clearing the relevant mode,
the procedure must be started again from initialization. Figure 11-23 shows a sample flowchart
for mode transition during transmission. Port pin states are shown in figures 11-24 and 11-25.
Operation should also be stopped (by clearing TE, TIE, and TEIE to 0) before making a
transition from transmission by DTC transfer to module stop mode or software standby mode
transition. To perform transmission with the DTC after the relevant mode is cleared, setting
TE and TIE to 1 will set the TXI flag and start DTC transmission.
448
t
LSB
D0 D1 D2 D3 D4 D5 D6 D7