C505_9708 SIEMENS [Siemens Semiconductor Group], C505_9708 Datasheet - Page 167

• Manufacturer Part Number: C505_9708
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

6.5.4 A/D Converter Timing
An A/D conversion is started by writing into special function register ADST. A write-to-ADST will
start a new conversion even if a conversion is currently in progress. The conversion begins with the
next machine cycle and the busy flag BSY will be set. The A/D conversion procedure is divided into
three parts:
The total A/D conversion time is defined by t
t
parameter as shown in figure 6-44.
Figure 6-44
A/D Conversion Timing
Semiconductor Group
CO
– Sample phase (t
– Conversion phase (t
– Write result phase (t
. The duration of the three phases of an A/D conversion is specified by its specific timing
Prescalar Ratio
(=PS)
32
16
8
4
BSY Bit
AD conversion
Start of an
S
), used for sampling the analog input voltage.
Sample
CO
WR
Phase
t
t
2 x PS x t
64 x t
32 x t
16 x t
), used for the A/D conversion.
S
), used for writing the conversion result into the ADDAT register.
S
8 x t
=
IN
IN
IN
IN
A/D Conversion Time Cycle Time
IN
t
t
ADCC
IN
8 x PS x t
256 x t
128 x t
t =
64 x t
32 x t
ADCC
Conversion Phase
OSC
t =
t
6-105
t
ADCC
CO =
S
+
IN
IN
IN
IN
which is the sum of the two phase times t
t
CO
t
IN
CO
On-Chip Peripheral Components
320 x t
160 x t
80 x t
40 x t
t
ADCC
Conversion Time
IN
IN
IN
IN
Result is written
53 + 2 x t
26 + 4 x t
13 + 2 x t
into ADDAT
n
6 + 4 x t
CPU Cycles
t
t
Time Ref.
WR
WR
IN
IN
IN
IN
C505 / C505C
MCT03300
=
Write
Result
Phase
3
2
a)
b)
a)
b)
t
IN
1997-08-01
S
and