參數(shù)資料
型號: MC68HC05L1FU
廠商: MOTOROLA INC
元件分類: 微控制器/微處理器
英文描述: 8-BIT, MROM, 2.1 MHz, MICROCONTROLLER, PQFP64
封裝: QFP-64
文件頁數(shù): 25/102頁
文件大?。?/td> 632K
代理商: MC68HC05L1FU
MC68HC05L1
MOTOROLA
4-1
RESETS AND INTERRUPTS
4
RESETS AND INTERRUPTS
4.1
RESETS
The MC68HC05L1 can be reset in two ways: by the initial power-on reset function and by an active
low input to the RESET pin. Any of these resets will cause the program to go to its starting
address, specied by the contents of memory locations $1FFE and $1FFF, and cause the interrupt
mask of the Condition Code register to be set.
4.1.1
RESET Pin
The RESET input pin is used to reset the MCU to provide an orderly software start-up procedure.
When using the external reset, the RESET pin must stay low for a minimum of 1.5tcyc. The
RESET pin contains an internal Schmitt Trigger as part of its input to improve noise immunity.
4.1.2
Power-On Reset (POR)
The power-on reset occurs when a positive transition is detected on the supply voltage, VDD. The
power-on reset is used strictly for power-up conditions, and should not be used to detect any drops
in the power supply voltage. There is no provision for a power-down reset. The power-on circuitry
provides for a 4064 tcyc delay from the time that the oscillator becomes active. If the external
RESET pin is low at the end of the 4064 tcyc time out, the processor remains in the reset condition
until RESET goes high. The user must ensure that VDD has risen to a point where the MCU can
operate properly prior to the time the 4064 POR cycles have elapsed. If there is doubt, the external
RESET pin should remain low until such time that VDD has risen to the minimum operating voltage
specied.
Table 4-1 shows the internal circuit actions on reset, but not necessary in order of occurrence.
TPG
27
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