H8S2245 datasheet(509/818 Pages) RENESAS

509 / 818 page

Section 12 Serial Communication Interface (SCI)

Rev.3.00 Mar. 26, 2007 Page 467 of 772

REJ09B0355-0300

Restrictions Concerning DTC Updating

• When an external clock source is used as the serial clock, the transmit clock should not be

input until at least 5

φ clock cycles after TDR is updated by the CPU and DTC. Misoperation

may occur if the transmit clock is input within 4

φ clocks after TDR is updated. (Figure 12.22)

• When RDR is read by the DTC, be sure to set the activation source to the relevant SCI

reception end interrupt (RXI).

• The flag is cleared only when DISEL in DTC is 0 with the transfer counter not being 0. When

DISEL is 1,or DISEL is 0 with the transfer counter being 0, the flag should be cleared by CPU.

Note that transmitting, in particular, may not successfully be executed unless the TDRE flag is

cleared by CPU.

LSB

Serial data

SCK

Note: When operating on an external clock, set t >4 clocks.

TDRE

Figure 12.22 Example of Clocked Synchronous Transmission by 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 12.23 shows a sample flowchart

for mode transition during transmission. Port pin states are shown in figures 12.24 and 12.25.

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

H8S2245 Datasheet(PDF) 509 Page - Renesas Technology Corp