HD643303x Hitachi, HD643303x Datasheet - Page 400

• Manufacturer Part Number: HD643303x
• Description: Hitachi Microcomputer
• Manufacturer: Hitachi

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
conversion timing. Table 12-4 indicates the A/D conversion time.
As indicated in figure 12-5, the A/D conversion time includes t
length of t
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.
ø
Address bus
Write signal
Input sampling
timing
ADF
Legend
(1):
(2):
t :
t
t
D
SPL
CONV
D
varies depending on the timing of the write access to ADCSR. The total conversion
:
:
D
ADCSR write cycle
ADCSR address
Synchronization delay
Input sampling time
A/D conversion time
after the ADST bit is set to 1, then starts conversion. Figure 12-5 shows the A/D
(1)
(2)
t
D
Figure 12-5 A/D Conversion Timing
t
SPL
385
t
CONV
D
and the input sampling time. The