mcf51ac256 Freescale Semiconductor, Inc, mcf51ac256 Datasheet - Page 28

• Manufacturer Part Number: mcf51ac256
• Description: Mcf51ac256 Coldfire Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

2.11
This section describes ac timing characteristics for each peripheral system.
1
2
3
4
5
6
7
Num C
19
20
21
22
TRIM register at default value (0x80) and FTRIM control bit at default value (0x0).
This specification applies to any time the FLL reference source or reference divider is changed, trim value changed or changing
from FLL disabled (BLPE, BLPI) to FLL enabled (FEI, FEE, FBE, FBI). If a crystal/resonator is being used as the reference,
this specification assumes it is already running.
This specification applies to any time the PLL VCO divider or reference divider is changed, or changing from PLL disabled
(BLPE, BLPI) to PLL enabled (PBE, PEE). If a crystal/resonator is being used as the reference, this specification assumes it
is already running.
Jitter is the average deviation from the programmed frequency measured over the specified interval at maximum f
Measurements are made with the device powered by filtered supplies and clocked by a stable external clock signal. Noise
injected into the FLL circuitry via V
a given interval.
625 ns represents 5 time quanta for CAN applications, under worst case conditions of 8 MHz CAN bus clock, 1 Mbps CAN bus
speed, and 8 time quanta per bit for bit time settings. 5 time quanta is the minimum time between a synchronization edge and
the sample point of a bit using 8 time quanta per bit.
Below D
is already in lock, then the MCG may stay in lock.
Below D
Table 16. MCG Frequency Specifications (continued)(Temperature Range = –40 to 125°C Ambient)
D Lock exit frequency tolerance
D Lock time — FLL
D Lock time — PLL
D
lock
Loss of external clock minimum
frequency – RANGE = 0
unl
AC Characteristics
minimum, the MCG will not exit lock if already in lock. Above D
minimum, the MCG is guaranteed to enter lock. Above D
Rating
DD
and V
7
SS
and variation in crystal oscillator frequency increase the C
Symbol
t
f
t
pll_lock
loc_low
fll_lock
D
unl
o
lock
maximum, the MCG will not enter lock. But if the MCG
(3/5) x f
unl
±4.47
Min
maximum, the MCG is guaranteed to exit lock.
—
—
int
Typical
—
—
—
—
1075(1/
1075(1/
t
t
pll_acquire+
fll_acquire+
±5.97
Max
Jitter
—
f
pll_ref)
f
int_t)
percentage for
BUS
Unit
.
kHz
%
s
s