ML63611 User’s Manual
Chapter 2 CPU and Memory Spaces
2 – 5
OPTION B (D): 1.5 V (3.0 V), With regulator
circuit for LCD bias
OPTION A (C): 1.5 V (3.0 V), Without regulator
circuit for LCD bias
2.2.7 Stack Pointer (SP) and Call Stack
The stack pointer (SP) is a pointer that indicates the call stack address where the program counter is saved when a
subroutine call or interrupt occurs.
The SP is a 4-bit up/down counter that is incremented during stack saves and is decremented during stack restores.
The call stack has 16 levels from address 0H to address 0FH. Because the hardware requires 1 level of the call
stack during program execution, only 15 levels can be used for stack saves. The contents of the call stack cannot
be read or written by the program.
Figure 2-3 shows the relation between SP and the call stack.
Figure 2-3 Relation between SP and Call Stack
SP is assigned to special function register (SFR) address 0F7H.
At system reset, SP is initialized to “0” and points to address “0H” of the call stack. SP is a read-only register and
writes are invalid.
3
2
1
0
SP
Stack pointer
Call stack
0FH
16 levels
0H
15 bits
SP3
SP2
SP1
SP0
SP (0F7H)
(R)
bit 3
bit 2
bit 1
bit 0
Содержание ML63611
Страница 9: ...Chapter 1 Overview...
Страница 33: ...Chapter 2 CPU and Memory Spaces...
Страница 42: ...Chapter 3 CPU Control Functions...
Страница 49: ...Chapter 4 Interrupt INT...
Страница 62: ...Chapter 5 Clock Generator Circuit OSC...
Страница 71: ...Chapter 6 Time Base Counter TBC...
Страница 75: ...Chapter 7 Timers TIMER...
Страница 99: ...Chapter 8 100 Hz Timer Counter 100HzTC...
Страница 103: ...Chapter 9 Watchdog Timer WDT...
Страница 108: ...Chapter 10 Ports INPUT I O PORT...
Страница 140: ...Chapter 11 Melody Driver MELODY...
Страница 152: ...Chapter 12 Serial Port SIO...
Страница 179: ...Chapter 13 LCD Driver LCD...
Страница 200: ...Chapter 14 Battery Low Detect Circuit BLD...
Страница 204: ...Chapter 15 Power Supply Circuit POWER...
Страница 215: ...Chapter 16 A D Converter ADC...
Страница 238: ...Appendixes...
Страница 271: ...ML63611 User s Manual First Edition May 2001 Second Edition June 2001 2001 Oki Electric Industry Co Ltd PEUL63611 02...