4513_03 Datasheet, PDF (59/210 Pages) Renesas Technology Corp – 4-BIT SINGLE-CHIP MICROCOMPUTER

HARDWARE
FUNCTION BLOCK OPERATIONS
(15) Notes for the use of A-D conversion 2
Do not change the operating mode (both A-D conversion mode and
comparator mode) of A-D converter with bit 3 of register Q2 while
A-D converter is operating.
When the operating mode of A-D converter is changed from the
comparator mode to A-D conversion mode with the bit 3 of register
Q2, note the following;
• Clear bit 2 of register V2 to “0” to change the operating mode of
the A-D converter from the comparator mode to A-D conversion
mode with the bit 3 of register Q2.
• The A-D conversion completion flag (ADF) may be set when the
operating mode of the A-D converter is changed from the com-
parator mode to the A-D conversion mode. Accordingly, set a
value to register Q2, and execute the SNZAD instruction to clear
the ADF flag.
(16) Definition of A-D converter accuracy
The A-D conversion accuracy is defined below (refer to Figure 30).
• Relative accuracy
ΠZero transition voltage (V0T)
This means an analog input voltage when the actual A-D con-
version output data changes from “0” to “1.”
 Full-scale transition voltage (VFST)
This means an analog input voltage when the actual A-D con-
version output data changes from “1023” to ”1022.”
Ž Linearity error
This means a deviation from the line between V0T and VFST of
a converted value between V0T and VFST.
 Differential non-linearity error
This means a deviation from the input potential difference re-
quired to change a converter value between V0T and VFST by 1
LSB at the relative accuracy.
• Absolute accuracy
This means a deviation from the ideal characteristics between 0
to VDD of actual A-D conversion characteristics.
Output data
1023
Full-scale transition voltage (VFST)
1022
Differential non-linearity error = ^b–a
a
[LSB]
Linearity error =
c
a
[LSB]
b
a
n+1
n
Actual A-D conversion
characteristics
c
a: 1LSB by relative accuracy
b: Vn+1–Vn
c: Difference between ideal Vn
and actual Vn
1
0
V0 V1
Zero transition voltage (V0T)
Fig. 30 Definition of A-D conversion accuracy
Ideal line of A-D conversion
between V0–V1022
Vn Vn+1
V1022
VDD
Analog voltage
Vn: Analog input voltage when the output data changes from “n” to “n+1” (n = 0 to 1022)
• 1LSB at relative accuracy → ^{VFST–V0T} (V)
1022
• 1LSB at absolute accuracy → ^VDD (V)
1024
1-46
4513/4514 Group User’s Manual