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4513_03 Datasheet, PDF (56/210 Pages) Renesas Technology Corp – 4-BIT SINGLE-CHIP MICROCOMPUTER | |||
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HARDWARE
FUNCTION BLOCK OPERATIONS
(7) Operation description
A-D conversion is started with the A-D conversion start instruction
(ADST). The internal operation during A-D conversion is as follows:
 When A-D conversion starts, the register AD is cleared to
â00016.â
 Next, the topmost bit of the register AD is set to â1,â and the
comparison voltage Vref is compared with the analog input volt-
age VIN.
 When the comparison result is Vref < VIN, the topmost bit of the
register AD remains set to â1.â When the comparison result is
Vref > VIN, it is cleared to â0.â
The 4513/4514 Group repeats this operation to the lowermost bit of
the register AD to convert an analog value to a digital value. A-D
conversion stops after 62 machine cycles (46.5 µs when f(XIN) =
4.0 MHz in high-speed mode) from the start, and the conversion re-
sult is stored in the register AD. An A-D interrupt activated condition
is satisfied and the ADF flag is set to â1â as soon as A-D conversion
completes (Figure 27).
Table 16 Change of successive comparison register AD during A-D conversion
At starting conversion
1st comparison
2nd comparison
3rd comparison
Change of successive comparison register AD
-------------
1
0
0 ----- 0
0
0
-------------
-------------
U1
1
0 ----- 0
0
0
-------------
-------------
U1 U2
1 ----- 0
0
0
-------------
After 10th comparison
completes
A-D conversion result
-------------
U1 U2 U3 ----- U8 U9 UA
-------------
U1: 1st comparison result
U3: 3rd comparison result
U9: 9th comparison result
U2: 2nd comparison result
U8: 8th comparison result
UA: 10th comparison result
VDD
2
VDD
2
VDD
2
VDD
2
Comparison voltage (Vref) value
VDD
±
4
VDD
VDD
± 4 ±8
±
â
â
â
â
±
VDD
1024
4513/4514 Group Userâs Manual
1-43
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