MC68HC705J1A

Manufacturer Part NumberMC68HC705J1A
ManufacturerMotorola
MC68HC705J1A datasheet
 


Specifications of MC68HC705J1A

CaseDIP-20L  
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Page 49/162

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3.5.3 Stack Pointer
The stack pointer (SP) is a 16-bit register that contains the address of
the next location on the stack. During a reset or after the reset stack
pointer instruction (RSP), the stack pointer is preset to $00FF. The
address in the stack pointer decrements after a byte is stacked and
increments before a byte is unstacked.
Read:
Write:
Reset:
The 10 most significant bits of the stack pointer are permanently fixed at
0000000011, so the stack pointer produces addresses from $00C0 to
$00FF. If subroutines and interrupts use more than 64 stack locations,
the stack pointer wraps around to address $00FF and begins writing
over the previously stored data. A subroutine uses two stack locations;
an interrupt uses five locations.
MC68HC705J1A — Rev. 4.0
MOTOROLA
Bit
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0
0
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0
= Unimplemented
Figure 3-4. Stack Pointer (SP)
Central Processor Unit (CPU)
Central Processor Unit (CPU)
CPU Registers
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1
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1
Technical Data
Bit
1
0
1
1
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