C504 SIEMENS [Siemens Semiconductor Group], C504 Datasheet - Page 27

• Manufacturer Part Number: C504
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

The A/D converter uses two clock signals for operation : the conversion clock f
the input clock f
is applied at the XTAL pins. The duration of an A/D conversion is a multiple of the period of the f
clock signal. The table in figure 10 shows the prescaler ratios and the resulting A/D conversion
times which must be selected for typical system clock rates.
Figure 10
A/D Converter Clock Selection
The analog inputs are located at port 1 and port 3 (4 lines on each port). The corresponding port 1
and port 3 pins have a port structure, which allows to use it either as digital I/Os or analog inputs.
The analog input function of these mixed digital/analog port lines is selected via the registers
P1ANA and P3ANA.
Semiconductor Group
MCU System Clock
Rate (f
3.5 MHz
12 MHz
16 MHz
24 MHz
32 MHz
40 MHz
OSC
IN
)
(= 1/ t
IN
f
[MHz]
1.75
6
8
12
16
20
). Both clock signals are derived from the C504 system clock f
IN
Ratio
4
4
4
8
8
16
Prescaler
27
ADCL1 ADCL0
0
0
0
0
0
1
0
0
0
1
1
0
f
[MHz]
.438
1.5
2
1.5
2
1.25
ADC
ADC
A/D Conversion
48 x t
48 x t
48 x t
96 x t
96 x t
192 x t
Time [ s]
(= 1/ t
IN
IN
IN
IN
IN
IN
= 27.4
= 8
= 6
= 8
= 6
OSC
= 9.6
ADC
C504
which
) and
IN