SAH-C515 SIEMENS [Siemens Semiconductor Group], SAH-C515 Datasheet - Page 105

• Manufacturer Part Number: SAH-C515
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

6.4.2.4
The C515 has two pins to which a reference voltage range for the on-chip A/D converter is applied
(pin
D converters it is now possible to use not only these externally applied reference voltages for the
conversion but also internally generated reference voltages which are derived from the externally
applied ones. For this purpose a resistor ladder provides 16 equidistant voltage levels between
V
the converter itself. These internally generated reference voltages are called
The internal reference voltage programming can be thought of as a programmable "D/A converter"
which provides the voltages
Special Function Register DAPR (Address DA H ) )
Bit
DAPR.7-.4
DAPR.3-.0
Any write-access to DAPR starts conversion.
The SFR DAPR is provided for programming the internal reference voltages
this purpose the internal reference voltages can be programmed in steps of 1/16 of the external
reference voltages (
while bits 4 to 7 specify
reference voltages
example, in the case where
between the internal reference voltages
The values of
Semiconductor Group
V
with DAPR.3-.0 < C H ;
V
with DAPR.7-.4 > 3 H ;
AREF
IntAGND
IntAREF
V
and
AREF
DA H
Bit No. MSB
=
=
V
Programmable Reference Voltages of the A/D Converter (DAPR Register)
V
V
for the upper voltage and pin
AGND
AGND
AGND
V
. These steps can individually be assigned as upper and lower reference voltage for
+
IntAGND
+
.7
7
Function
Programming of
These bits are used for adjustment of the internal
Programming of
These bits are used for adjustment of the internal
DAPR.3-.0
DAPR.7-.4
V
V
lntARF
AREF
and
16
16
.6
V
6
–
and
V
IntAREF
V
IntAREF
V
V
AREF
AGND
IntARFF
V
IntAGND
. A minimum of 1 V difference is required between the internal
(
(
is 5 V and
are given by the formulas:
V
V
) by four bits each in register DAPR. Bits 0 to 3 specify
.5
5
AREF
AREF
and
V
V
IntAREF
IntAGND
for proper operation of the A/D converter. This means, for
–
–
V
V
V
V
V
AGND
IntAGND
IntAREF
.4
AGND
AGND
4
V
AGND
for the lower voltage). In contrast to conventional A/
)
)
6-62
and
for the A/D converter itself.
is 0 V, there must be at least four steps difference
.3
3
V
IntAGND
On-Chip Peripheral Components
.
.2
2
.1
1
V
V
IntAREF
IntAGND
LSB
V
.0
voltage.
IntAREF
voltage.
0
V
Reset Value : 00 H
lntAREF
and
DAPR
and
V
lntAGND
V
V
C515
lntAGND
lntAGND
. For
.
,