HD404459 Datasheet, PDF (86/122 Pages) Renesas Technology Corp – 4-bit HMCS400-series microcomputers

HD404459 Series
Operating States: The serial interface has the following operating states, which allow transitions to occur
between them (figure 68).
 STS wait state
 Transmit clock wait state
 Transfer state
Continuous clock output state (only in internal clock mode)
External clock mode
STS wait state
(Octal counter = 000,
transmit clock disabled)
00 MCU reset
SMRA write 04
01 STS instruction
06 SMRA write (IFS ^← 1)
Transmit clock wait state
(Octal counter = 000)
02 Transmit clock
03
8 transmit clocks
05
STS instruction (IFS ^← 1)
Transfer state
(Octal counter = 000)
Internal clock mode
SMRA write
18
STS wait state
(Octal counter = 000,
transmit clock disabled)
10 MCU reset
Continuous clock output state
(PMRA 0, 1 = 0, 0)
SMRA write 14
11 STS instruction
Transmit clock 17
Transmit clock wait state
(Octal counter = 000)
12 Transmit clock
15
STS instruction (IFS ← 1)
13 8 transmit clocks
16 SMRA write (IFS ←1)
Transfer state
(Octal counter = 000)
Note: Refer to the Operating States section for the explanations on the corresponding encircled numbers.
Figure 68 Serial Interface State Transitions
• STS wait state: The serial interface enters STS wait state by MCU reset (00 and 10 in figure 68). In STS
wait state, the serial interface is initialized and the transmit clock is ignored. If the STS instruction is
then executed (01 and 11), the serial interface enters transmit clock wait state.
84