MC56F8257MLH Freescale Semiconductor, MC56F8257MLH Datasheet - Page 121

• 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

Setting both SE and FILT_PER to 0 disables the filter and eliminates switching current
associated with the filtering process. Always switch to this setting before changing any
filter parameters. It resets the filter to a known state. Switching the FILTER_CNT field
on the fly without this intermediate step can result in unexpected behavior.
If SE is 1, the filter takes samples of COUTA on each positive transition of the SAMPLE
input. The output state of the filter changes when the FILTER_CNT field's consecutive
samples all agree that the output value has changed.
3.6.5.3 Latency Issues
The FILT_PER field's value (or SAMPLE period) should be set such that the sampling
period is just larger the period of the expected noise. This way a noise spike corrupts only
one sample. The FILTER_CNT field's value should be chosen to reduce the probability
of noisy samples causing an incorrect transition to be recognized. The probability of an
incorrect transition is defined as the probability of an incorrect sample raised to the power
of the FILTER_CNT field's value.
The following table summarizes maximum latency values for the various modes of
operation in the absence of noise. Filtering latency is restarted each time an actual output
transition is masked by noise.
The values of the FILT_PER field (or SAMPLE period) and the FILTER_CNT field
must also be balanced against the desire for minimal latency in recognizing actual
comparator output transitions. The probability of detecting an actual output change within
the nominal latency is the probability of a correct sample raised to the power of the
FILTER_CNT field's value.
Freescale Semiconductor
Mode
2A
2B
3A
3B
4A
4B
5A
5B
1
EN
0
1
1
1
1
1
1
1
1
WE
X
0
0
0
0
0
0
1
1
Table 3-23. Comparator Sample/Filter Maximum Latencies
SE
X
0
0
1
0
1
0
0
0
FILTER_CNT FILT_PER
> 0x1
> 0x1
MC56F825x/4x Reference Manual, Rev. 2, 10/2010
0x0
0x1
0x1
0x0
X
X
X
Table continues on the next page...
> 0x0
> 0x0
0x00
0x00
X
X
X
X
X
Preliminary
Sampled, Non-
Filtered mode
Sampled, Fil‐
Continuous
tered mode
Windowed
Operation
Disabled
mode
Mode
T
PD
Chapter 3 High Speed Comparator (HSCMP)
T
+ (FILTER_CNT X FILT_PER X T
PD
T
+ (FILTER_CNT X T
PD
+ (FILT_PER X T
T
Maximum Latency
PD
+ T
T
T
PD
PD
SAMPLE
N/A
T
+ T
+ T
PD
per
per
+ T
SAMPLE
per
per
) + T
1
) + T
per
per
) + T
per
per
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