MC56F8257MLH Freescale Semiconductor, MC56F8257MLH Datasheet - Page 120

• Manufacturer Part Number: MC56F8257MLH
• Description: DSC 64K FLASH 60MHZ 64-LQFP
• Manufacturer: Freescale Semiconductor
• Series: 56F8xxxr

Specifications of MC56F8257MLH

• Core Processor: 56800E
• Core Size: 16-Bit
• Speed: 60MHz
• Connectivity: CAN, I²C, LIN, SCI, SPI
• Peripherals: LVD, POR, PWM, WDT
• Number Of I /o: 54
• Program Memory Size: 64KB (32K x 16)
• Program Memory Type: FLASH
• Ram Size: 4K x 16
• Voltage - Supply (vcc/vdd): 3 V ~ 3.6 V
• Data Converters: A/D 16x12b, D/A 1x12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 105°C
• Package / Case: 64-LQFP
• Product: DSCs
• Processor Series: 56800E
• Core: 56800E
• Device Million Instructions Per Second: 60 MIPs
• Maximum Clock Frequency: 60 MHz
• Number Of Programmable I/os: 54
• Data Ram Size: 8 KB
• Operating Supply Voltage: 3.3 V
• Maximum Operating Temperature: + 105 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 12 bit, 8 Channel
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / Rohs Status: Details

Low Pass Filter
During operation, the propagation delay of the selected data paths must always be
considered. It can take many peripheral bus clock cycles for COUT and the CFR/CFF
status bits to reflect an input change or a configuration change to one of the components
involved in the data path.
When programmed for filtering modes, COUT is initially equal to zero until sufficient
clock cycles have elapsed to fill all stages of the filter. This occurs even if COUTA is at a
one.
3.6.5
Low Pass Filter
3.6.5.1 Introduction
The low-pass filter operates on the unfiltered, unsynchronized, and optionally-inverted
comparator output COUTA and generates the filtered and synchronized output COUT.
Both COUTA and COUT can be configured as module outputs and are used for different
purposes within the system.
Synchronization and edge detection are always used to determine status register bit
values. They also apply to COUT for all sampling and windowed modes. Filtering can be
performed using an internal timebase defined by the FPR[FILT_PER] field or by using
an external SAMPLE input to determine sample time.
The need for digital filtering and the amount of filtering is dependent on user
requirements. Filtering can become more useful in the absence of an external hysteresis
circuit. Without external hysteresis, high frequency oscillations can be generated at
COUTA when the selected N and P input voltages differ by less than the offset voltage of
the differential comparator.
3.6.5.2 Enabling Filter Modes
Filter modes are enabled by setting the CR0[FILTER_CNT] field to be greater than 0x1
and setting the FPR[FILT_PER] to a non-zero value or setting SE to 1. If the divided
peripheral clock is driving the filter, it takes samples of COUTA every FILT_PER
peripheral bus cycles.
The filter output is at zero when first initialized and subsequently changes when the
FILTER_CNT field's consecutive samples all agree that the output value has changed.
Said another way, COUT is zero for some initial period, even when COUTA is at one.
MC56F825x/4x Reference Manual, Rev. 2, 10/2010
Preliminary
120
Freescale Semiconductor