
CHAPTER 15 SERIAL INTERFACE CHANNEL 1
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(a) In case the automatic data transmit/receive function is performed by an internal clock
The internal clock operation is performed when bit 1 (CSIM11) of the serial operating mode register
1 (CSIM1) is set to 1.
In this case, the interval is determined as follows by CPU processing.
When bit 7 (ADTI7) of the automatic data transmit/receive interval specify register (ADTI) is set to 0,
the interval is determined by CPU processing. When ADTI7 is set to 1, the interval is determined by
the contents of ADTI or by CPU processing, whichever is greater. For the interval determined by ADTI,
see the format shown in Figure 15-5. Automatic Data Transmit/Receive Interval Specify Register
Format.
Table 15-3. Interval Time by CPU Processing (During Internal Clock Operation)
CPU Processing
Interval
When using multiplication instruction
MAX. (2.5 T
SCK
, 13 T
CPU
)
When using division instruction
MAX. (2.5 T
SCK
, 20 T
CPU
)
External, access 1 wait mode
MAX. (2.5 T
SCK
, 9 T
CPU
)
Other than above
MAX. (2.5 T
SCK
, 7 T
CPU
)
T
SCK
: 1/f
SCK
f
SCK
: Serial clock frequency
T
CPU
: 1/f
CPU
f
CPU
: CPU clock (set by bits 0 to 2 (PCC0 to PCC2) of the processor clock control register (PCC)
MAX. (a, b) : a or b, whichever is greater
Figure 15-24. Operation Timing with Automatic Data Transmit/Receive
Function Performed by Internal Clock
f
X
f
CPU
(n = 1)
SCK1
SO1
SI1
T
CPU
T
SCK
Interval
D7
D6
D5
D4
D3
D2
D1
D0
D7
D6
D5
D4
D3
D2
D1
D0
f
X
: Main system clock oscillation frequency
f
CPU
: CPU clock (set by bits 0 to 2 (PCC0 to PCC2) of the processor clock control register (PCC)
T
CPU
: 1/f
CPU
T
SCK
: 1/f
SCK
f
SCK
: Serial clock frequency