Rev. 1.0, 09/02, page 435 of 568
17.4.3
Input Sampling and A/D Conversion Time
The A/D converter includes the sample-and-hold circuit. The A/D converter samples the analog
input when the A/D conversion start delay time (t
D
) has passed after the ADST bit is set to 1, and
then conversion is started. Figure 17.2 shows the A/D conversion timing. Table 17.3 shows the
A/D conversion time.
As shown in figure 17.2, the A/D conversion time (t
CONV
) includes t
D
and input sampling time (t
SPL
).
The length of t
D
varies depending on the timing of the write access to ADCSR. Therefore, the total
conversion time varies within the range shown in table 17.3.
In scan mode, the values given in table 17.3 indicate the first conversion time. The second and
subsequent conversion time is shown in table 17.4. In both cases, set bits CKS1 and CKS0 in
ADCR within the range shown in table 23.7 in section 23, Electrical Characteristics.
(1)
(2)
t
D
t
SPL
t
CONV
φ
Address
Write signal
Input sampling
timing
ADF
Legend
(1)
: ADCSR write cycle
(2)
: ADCSR address
t
D
: A/D conversion start delay
t
SPL
: Input sampling time
t
CONV
: A/D conversion time
Figure 17.2 A/D Conversion Timing
Содержание H8S/2627
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