mcf51ac256a Freescale Semiconductor, Inc, mcf51ac256a Datasheet - Page 169

• Manufacturer Part Number: mcf51ac256a
• Description: Mcf51ac Flexis
• Manufacturer: Freescale Semiconductor, Inc

9.1.3
9.1.3.1
The ADCSC1[COCO] bit of the ADC module can be used as one of the three FTM hardware
synchronization triggers. This ADC input is the highest priority of the three hardware sync triggers.
9.1.3.2
The ACMP1 module has the capability to send a hardware trigger to the ADC using the ACMP1SC[ACF]
bit. The ADC hardware trigger is enabled by the ADCSC2[ADTRG] bit. In addition, the hardware trigger
source must be selected with the SOPT2[ADHWTS1:ADHWTS0] bits. ADHWTS1:ADHWTS0 = 0b01
selects ACMP1 as the ADC hardware trigger.
Typical usage is for the ACMP to be constantly monitoring a voltage level and the ADC to be off or
monitoring a different signal until a voltage of interest is observed on the ACMP1 input. The ADC can
then measure the same signal for a more accurate reading. Since ACMP1– and AD1P9 share the same pin
as do ACMP1+ and AD1P8, taking an ADC reading on the ACMP1 inputs is trivial and doesn’t require
separate pins for ACMP1 and ADC.
9.1.3.3
The FTM1 module has the capability to send a hardware trigger to the ADC using the
FTM1_ADC_TRIGGER register. FTM1 can be configured to send a trigger on any channel value match
from channels 2–5 (channels 0–1 cannot be used). Multiple channels can be selected at once to generate
multiple triggers to the ADC within one period of the FTM counter.
The ADC hardware trigger is enabled by the ADCSC2[ADTRG] bit. In addition, the hardware trigger
source must be selected with the SOPT2[ADHWTS] bits. ADHWTS = 0b10 selects the FTM1 as the ADC
hardware trigger.
9.1.3.4
The RTI module has the capability to send a hardware trigger to the ADC using the RTISC[RTIF] bit. The
ADC hardware trigger is enabled by the ADCSC2[ADTRG] bit. In addition, the hardware trigger source
must be selected with the SOPT2[ADHWTS] bits. ADHWTS = 0b00 selects the RTI as the ADC hardware
trigger.
Typical usage is to use the RTI to send a trigger to the ADC to provide a constant periodic monitoring of
the ADC input when configuring the ADC for continuos conversions is not desired. Since both the RTI
and ADC modules can run in stop and wait modes and by using the automatic compare function of the
ADC, periodic measurements can be made without waking the MCU from the low power mode until the
ADC result meets the compare condition.
Freescale Semiconductor
ADC Module Interconnects
ADC to FTMx synchronization triggers
ACMP1 to ADC Hardware Trigger
FTM1 to ADC Hardware Trigger
RTI to ADC Hardware Trigger
MCF51AC256 ColdFire Integrated Microcontroller Reference Manual, Rev. 5
Analog-to-Digital Converter (ADC12V1)
9-3