mc9s08sh8mwjr Freescale Semiconductor, Inc, mc9s08sh8mwjr Datasheet - Page 122

• Manufacturer Part Number: mc9s08sh8mwjr
• Description: S08sh 5-volt 8-bit Microcontrollers With Sci, Spi, I2c, Adc And Analog Comparators
• Manufacturer: Freescale Semiconductor, Inc

2
Chapter 9 Analog-to-Digital Converter (S08ADCV1)
9.1.2
References to V
9.1.3
The ADC module is capable of performing conversions using the MCU bus clock, the bus clock divided
by two, the local asynchronous clock (ADACK) within the module, or the alternate clock, ALTCLK. The
alternate clock for the MC9S08SH32 Series MCU devices is the external reference clock (ICSERCLK).
The selected clock source must run at a frequency such that the ADC conversion clock (ADCK) runs at a
frequency within its specified range (f
determined by the ADIV bits.
ALTCLK is active while the MCU is in wait mode provided the conditions described above are met. This
allows ALTCLK to be used as the conversion clock source for the ADC while the MCU is in wait mode.
ALTCLK cannot be used as the ADC conversion clock source while the MCU is in either stop2 or stop3.
9.1.4
The ADC hardware trigger, ADHWT, is the output from the real time counter (RTC). The RTC counter
can be clocked by either ICSERCLK, ICSIRCLK or a nominal 1 kHz clock source.
The period of the RTC is determined by the input clock frequency, the RTCPS bits, and the RTCMOD
register. When the ADC hardware trigger is enabled, a conversion is initiated upon an RTC counter
overflow. The RTIE does not have to be set for RTC to cause a hardware trigger.
The RTC can be configured to cause a hardware trigger in MCU run, wait, and stop3.
9.1.5
To use the on-chip temperature sensor, the user must perform the following:
122
Requires BGBE =1 in SPMSC1 see
For value of bandgap voltage reference see
•
•
•
Configure ADC for long sample with a maximum of 1 MHz clock
Convert the bandgap voltage reference channel (AD27)
— By converting the digital value of the bandgap voltage reference channel using the value of
Convert the temperature sensor channel (AD26)
— By using the calculated value of V
V
Characteristics”.
Analog Power and Ground Signal Names
Alternate Clock
Hardware Trigger
Temperature Sensor
BG
DDAD
the user can determine V
and V
SSAD
Section 5.7.6, “System Power Management Status and Control 1 Register
in this chapter correspond to signals V
MC9S08SH32 Series Data Sheet, Rev. 2
ADCK
A.6, “DC
DD
) after being divided down from the ALTCLK input as
. For value of bandgap voltage, see
PRELIMINARY
DD
Characteristics”.
, convert the digital value of AD26 into a voltage,
DDA
and V
Section A.6, “DC
SSA
Freescale Semiconductor
, respectively.
(SPMSC1)”.
V
TEMP