MC9S08JM16CGTE FREESCALE [Freescale Semiconductor, Inc], MC9S08JM16CGTE Datasheet - Page 150

• Manufacturer Part Number: MC9S08JM16CGTE
• Description: Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Analog-to-Digital Converter (S08ADC12V1)
10.4.4.5
The total conversion time depends on the sample time (as determined by ADLSMP), the MCU bus
frequency, the conversion mode (8-bit, 10-bit or 12-bit), and the frequency of the conversion clock (
After the module becomes active, sampling of the input begins. ADLSMP selects between short (3.5
ADCK cycles) and long (23.5 ADCK cycles) sample times.When sampling is complete, the converter is
isolated from the input channel and a successive approximation algorithm is performed to determine the
digital value of the analog signal. The result of the conversion is transferred to ADCRH and ADCRL upon
completion of the conversion algorithm.
If the bus frequency is less than the f
cannot be guaranteed when short sample is enabled (ADLSMP=0). If the bus frequency is less than 1/11th
of the f
sample is enabled (ADLSMP=1).
The maximum total conversion time is determined by the clock source chosen and the divide ratio selected.
The clock source is selectable by the ADICLK bits, and the divide ratio is specified by the ADIV bits. For
example, in 10-bit mode, with the bus clock selected as the input clock source, the input clock divide-by-1
ratio selected, and a bus frequency of 8 MHz, then the conversion time for a single conversion is:
150
The maximum total conversion time for different conditions is summarized in
Single or first continuous 10-bit or 12-bit
Single or first continuous 10-bit or 12-bit
Single or first continuous 10-bit or 12-bit
Single or first continuous 10-bit or 12-bit
Subsequent continuous 10-bit or 12-bit;
Subsequent continuous 10-bit or 12-bit;
ADCK
Single or first continuous 8-bit
Single or first continuous 8-bit
Single or first continuous 8-bit
Single or first continuous 8-bit
Subsequent continuous 8-bit;
Subsequent continuous 8-bit;
frequency, precise sample time for continuous conversions cannot be guaranteed when long
Sample Time and Total Conversion Time
Conversion Type
f
f
BUS
BUS
f
f
BUS
BUS
> f
> f
> f
> f
ADCK
ADCK
ADCK
ADCK
Conversion time =
Table 10-13. Total Conversion Time vs. Control Conditions
/11
/11
Number of bus cycles = 3.5 μs x 8 MHz = 28 cycles
MC9S08JM16 Series Data Sheet, Rev. 2
ADCK
23 ADCK Cyc
frequency, precise sample time for continuous conversions
8 MHz/1
ADICLK
0x, 10
0x, 10
0x, 10
0x, 10
11
11
11
11
xx
xx
xx
xx
ADLSMP
+
0
0
1
1
0
0
1
1
0
0
1
1
5 bus Cyc
8 MHz
23 ADCK cycles + 5 bus clock cycles
43 ADCK cycles + 5 bus clock cycles
20 ADCK cycles + 5 bus clock cycles
40 ADCK cycles + 5 bus clock cycles
5 μs + 20 ADCK + 5 bus clock cycles
5 μs + 23 ADCK + 5 bus clock cycles
5 μs + 40 ADCK + 5 bus clock cycles
5 μs + 43 ADCK + 5 bus clock cycles
Max Total Conversion Time
= 3.5 μs
17 ADCK cycles
20 ADCK cycles
37 ADCK cycles
40 ADCK cycles
Table
Freescale Semiconductor
10-13.
f
ADCK
).