R01UH0822EJ0100 Rev.1.00
Page 872 of 1041
Jul 31, 2019
RX13T Group
26. 12-Bit A/D Converter (S12ADF)
26.3.5
Analog Input Sampling Time and Scan Conversion Time
shows the scan conversion timing in single scan mode, in which scan conversion is activated by software
or a synchronous trigger.
shows the scan conversion timing in single scan mode, in which scan conversion
is activated by an asynchronous trigger. The scan conversion time (t
SCAN
) includes the start-of-scanning-delay time (t
D
),
channel-dedicated sample-and-hold circuit processing time (t
SPLSH
)
, disconnection detection assistance processing
time (t
DIS
)
, self-diagnosis A/D conversion processing time (t
DIAG
, A/D conversion processing time (t
CONV
),
channel-dedicated sample-and-hold circuit end time (t
SHED
, and end-of-scanning-delay time (t
ED
).
The A/D conversion processing time (t
CONV
) consists of sampling time (t
SPL
) and time for conversion by successive
approximation (t
SAM
). The sampling time (t
SPL
) is used to charge sample-and-hold circuits in the A/D converter. If there
is not sufficient sampling time due to the high impedance of an analog input signal source, or if the A/D conversion clock
(ADCLK) is slow, sampling time can be adjusted using the ADSSTR register.
The time for conversion by successive approximation (t
SAM
shows the scan
conversion time.
The scan conversion time (t
SCAN
) in single scan mode for which the number of selected channels is n can be determined
as follows:
t
SCAN
= t
D
+ t
SPLSH
+ (t
DIS
× n) + t
DIAG
+ (t
CONV
× n)
+ t
ED
The scan conversion time for the first cycle in continuous scan mode is t
SCAN
for single scan minus t
ED
plus t
SHED
.
The scan conversion time for the second and subsequent cycles in continuous scan mode is fixed to t
SPLSH
+ (t
DIS
× n) +
t
DIAG
+ t
DSD
+ (t
CONV
× n)
+ t
SHED
.
Note 1. When no channel-dedicated sample-and-hold circuits are used, t
SPLSH
= 0.
Note 2. When disconnection detection assistance is not selected, t
DIS
= 0. The auto-discharge period of 15 ADCLK
states is inserted only when internal reference voltage is A/D-converted.
Note 3. When the self-diagnosis function is not used, t
DIAG
= 0, t
DSD
= 0.
Note 4. When no channel-dedicated sample-and-hold circuits are used, t
SHED
= 0. Here, continuous scan mode is
assumed. In single scan mode and group scan mode, t
SHED
is included in the end-of-scanning-delay time (t
ED
).
Note 5. t
CONV
× n when the sampling time (t
SPL
) of selected channels is the same, but it is the total of the sampling time
of each channel and time for conversion by successive approximation (t
SAM
).