C517A_99 Datasheet, PDF (161/218 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

On-Chip Peripheral Components
C517A
6.6.2 A/D Converter Registers
This section describes the bits/functions of all registers which are used by the A/D converter.
Special Function Registers ADDATH (Address D9H)
Special Function Registers ADDATL (Address DAH)
Bit No. MSB
7
6
5
4
3
2
D9H
MSB
.9
.8
.7
.6
.5
.4
Reset Value : 00H
Reset Value : 00XXXXXXB
LSB
1
0
.3
.2 ADDATH
DAH
.1
LSB
.0
–
–
–
–
–
– ADDATL
The registers ADDATH and ADDATL hold the 10-bit conversion result in left justified data format.
The most significant bit of the 10-bit conversion result is bit 7 of ADDATH. The least significant bit
of the 10-bit conversion result is bit 6 of ADDATL. To get a 10-bit conversion result, both ADDAT
register must be read. If an 8-bit conversion result is required, only the reading of ADDATH is
necessary. The data remain in ADDATH/ADDATL until it is overwritten by the next converted data.
ADDAT can be read or written under software control. lf the A/D converter of the C517A is not used,
register ADDATH can be used as an additional general purpose register.
Each A/D conversion is started by writing to SFR ADDATL with dummy data. If continuous
conversion is selected, ADDATL must be written only once to start continuous conversion.
Semiconductor Group
6-95