Datasheet

Table Of Contents
Section 16 A/D Converter
Page 610 of 846 REJ09B0140-0900 Rev. 9.00
Sep 16, 2010
H8S/2215 Group
ADST
ADF
ADDRA
ADDRB
ADDRC
ADDRD
State of channel 0 (AN0)
State of channel 1 (AN1)
State of channel 2 (AN2)
State of channel 3 (AN3)
Set*
1
Clear*
1
Idle
Notes: 1. Vertical arrows ( ) indicate instructions executed by software.
2. Data currently being converted is ignored.
Clear*
1
Idle
Idle
A/D conversion time
Idle
Continuous A/D conversion execution
A/D conversion 1
Idle
Idle
Idle
Idle
Idle
Transfer
*
2
A/D conversion 3
A/D conversion 2 A/D conversion 5
A/D conversion 4
A/D conversion result 1
A/D conversion result 2
A/D conversion result 3
A/D conversion result 4
Figure 16.4 A/D Conversion Timing (Scan Mode, Channels AN0 to AN3 Selected)
16.5.3 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 when the A/D conversion start delay time (t
D
) has passed after the ADST bit is set to 1, then
starts conversion. Figure 16.5 shows the A/D conversion timing. Tables 16.3 and 16.4 show the
A/D conversion time.
As indicated in figure 16.5, the A/D conversion time (t
CONV
) includes t
D
and the input sampling time
(t
SPL
). 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 16.4.
In scan mode, the values given in table 16.4 apply to the first conversion time. The values given in
table 16.5 apply to the second and subsequent conversions.