¡ Semiconductor
MSM80C48/49/50, MSM80C35/39/40
4.3 Hardware power-down mode
In the MSM80C48, MSM80C49 and MSM80C50, forcing the level at the V
pin to a "0"
DD
during either external ROM or internal ROM mode results in suspension of the oscillator
function and subsequent floating (high impedance) of all the I/O pins except the RESET,
SS and XTAL 1/2 pins. The CPU is thereby stopped while maintaining internal status.
4.4 Cancellation of hardware power-down mode
(1) Use of RESET pin
m
The clock generator is activated and the CPU started up when a "1" level is applied to
the V pin while a "0" level is input to the RESET pin. If this "0" level is kept applied
DD
to the RESET pin until oscillation become stable, the CPU will be reset and will start
executing from address 0.
(2) Use of the INT pin during external interrupt enable status (i.e. following execution of EN
I instruction)
m
The clock generator is activated and the CPU started up when a "1" level is applied to
the V
pin while a "0" level is applied to the INT pin. If this "0" level is maintained
DD
until the occurrence of at least 2 ALE output signals, an external interrupt is generated,
and execution starts from address 3.
However, if the power-down mode is started during an interrupt processing routine,
execution will be continued on the next instruction after the present instruction.
(3) Use of the INT pin during external interrupt disable mode (i.e. following excution of DIS
I instruction or hardware reset)
m
The clock generator is activated and the CPU started up when a "1" level is applied to
the V pin while a "0" level is applied to the INT pin. If this "0" level is maintained
DD
until the occurrence of at least 2 ALE output signals, execution is continued on the next
instruction after the present instruction.
(4) Use of V
pin only
DD
m
The clock generator is activated and the CPU started up when a "1" level is applied to
the V pin while a "1" level is also applied to both the RESET and INT pins. In this
DD
case, execution is resumed from the stopped position.
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