HD6432633 Datasheet, PDF (815/1453 Pages) Renesas Technology Corp – Series of Microcomputers (MCUs: microcomputer units)

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 16-24)
• When RDR is read by the DMAC* or DTC*, be sure to set the activation source to the relevant
SCI reception end interrupt (RXI).
SCK
TDRE
Serial data
t
LSB
D0
D1
D2
D3
D4
D5
D6
D7
Note: When operating on an external clock, set t >4 clocks.
Figure 16-24 Example of Clocked Synchronous Transmission by DTC*
Note: * DMAC and DTC functions are not available in the H8S/2695.
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, watch mode, subactive mode, or subsleep mode transition.
TSR, TDR, and SSR are reset. The output pin states in module stop mode, software standby
mode, watch mode, subactive 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 16-25 shows a sample flowchart
for mode transition during transmission. Port pin states are shown in figures 16-26 and 16-27.
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, software standby mode,
watch mode, subactive mode, or subsleep 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.
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