Datasheet

Table Of Contents
Section 13 Serial Communication Interface
REJ09B0140-0900 Rev. 9.00 Page 465 of 846
Sep 16, 2010
H8S/2215 Group
In particular, data transmission cannot be completed correctly unless the TDRE flag is cleared
using the CPU.
t
D0
LSB
Serial data
SCK
D1
D3 D4 D5D2 D6 D7
Note: When o
p
eratin
g
on an external clock, set t>4 clocks.
TDRE
Figure 13.39 Example of Clocked Synchronous Transmission by DMAC or DTC
13.10.5 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, software standby mode, or subsleep mode transition. TSR, TDR, and SSR are reset.
The output pin states in module stop mode, software standby mode, or subsleep 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
13.40 shows a sample flowchart for mode transition during transmission. Port pin states are
shown in figures 13.41 and 13.42.
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.