MC68376BGMAB20 Freescale Semiconductor, MC68376BGMAB20 Datasheet - Page 126

• Manufacturer Part Number: MC68376BGMAB20
• Description: IC MCU 32BIT 8K ROM 160-QFP
• Manufacturer: Freescale Semiconductor
• Series: M683xxr

Specifications of MC68376BGMAB20

• Core Processor: CPU32
• Core Size: 32-Bit
• Speed: 20MHz
• Connectivity: CAN, EBI/EMI, SCI, SPI
• Peripherals: POR, PWM, WDT
• Number Of I /o: 18
• Program Memory Type: ROMless
• Ram Size: 7.5K x 8
• Voltage - Supply (vcc/vdd): 4.75 V ~ 5.25 V
• Data Converters: A/D 16x10b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 160-QFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Program Memory Size: -

5.7.7 Power-On Reset
5-48
MOTOROLA
When an external device asserts RESET for the proper period, reset control logic
clocks the signal into an internal latch. The control logic drives the RESET pin low for
an additional 512 CLKOUT cycles after it detects that the RESET signal is no longer
being externally driven to guarantee this length of reset to the entire system.
If an internal source asserts a reset signal, the reset control logic asserts the RESET
pin for a minimum of 512 cycles. If the reset signal is still asserted at the end of 512
cycles, the control logic continues to assert the RESET pin until the internal reset sig-
nal is negated.
After 512 cycles have elapsed, the RESET pin goes to an inactive, high-impedance
state for ten cycles. At the end of this 10-cycle period, the RESET input is tested.
When the input is at logic level one, reset exception processing begins. If, however,
the RESET input is at logic level zero, reset control logic drives the pin low for another
512 cycles. At the end of this period, the pin again goes to high-impedance state for
ten cycles, then it is tested again. The process repeats until RESET is released.
When the SIM clock synthesizer is used to generate system clocks, power-on reset
involves special circumstances related to application of system and clock synthesizer
power. Regardless of clock source, voltage must be applied to the clock synthesizer
power input pin V
that V
When V
rameters and by oscillator circuit design. V
ing reset. Refer to APPENDIX A ELECTRICAL CHARACTERISTICS for voltage and
timing specifications.
During power-on reset, an internal circuit in the SIM drives the IMB internal (MSTRST)
and external (EXTRST) reset lines. The power-on reset circuit releases the internal re-
set line as V
ized to the values shown in Table 5-17. When V
voltage, the clock synthesizer VCO begins operation. Clock frequency ramps up to
specified limp mode frequency (f
the clock synthesizer PLL locks and 512 CLKOUT cycles elapse.
The SIM clock synthesizer provides clock signals to the other MCU modules. After the
clock is running and MSTRST is asserted for at least four clock cycles, these modules
reset. V
cles take. Worst case is approximately 15 milliseconds. During this period, module
port pins may be in an indeterminate state. While input-only pins can be put in a known
state by external pull-up resistors, external logic on input/output or output-only pins
during this time must condition the lines. Active drivers require high-impedance buffers
or isolation resistors to prevent conflict.
DDSYN
DD
DDSYN
ramp time and VCO frequency ramp time determine how long the four cy-
DD
is applied before and during reset, which minimizes crystal start-up time.
is applied at power-on, start-up time is affected by specific crystal pa-
ramps up to the minimum operating voltage, and SIM pins are initial-
DDSYN
for the MCU to operate. The following discussion assumes
SYSTEM INTEGRATION MODULE
limp
). The external RESET line remains asserted until
DD
ramp-up time also affects pin state dur-
DD
reaches the minimum operating
USER’S MANUAL
MC68336/376