HD6473032F Datasheet, PDF (400/572 Pages) Hitachi Semiconductor – Hitachi Microcomputer

12.4.3 Input Sampling and A/D Conversion Time
The A/D converter has a built-in sample-and-hold circuit. The A/D converter samples the analog
input at a time t_D after the ADST bit is set to 1, then starts conversion. Figure 12-5 shows the A/D
conversion timing. Table 12-4 indicates the A/D conversion time.
As indicated in figure 12-5, the A/D conversion time includes t_D and the input sampling time. The
length of t_D varies depending on the timing of the write access to ADCSR. The total conversion
time therefore varies within the ranges indicated in table 12-4.
In scan mode, the values given in table 12-4 apply to the first conversion. In the second and
subsequent conversions the conversion time is fixed at 256 states when CKS = 0 or 128 states
when CKS = 1.
(1)
ø
Address bus (2)
Write signal
Input sampling
timing
ADF
t_D
t _SPL
Legend
(1): ADCSR write cycle
(2): ADCSR address
t_D : Synchronization delay
t_SPL : Input sampling time
t_CONV: A/D conversion time
t _CONV
Figure 12-5 A/D Conversion Timing
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