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ML63326 User's Manual
Chapter 2 CPU and Memory Spaces
2
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.
3
2
1
0
SP
Stack pointer
Call stack
0FH
16 levels
0H
15 bits
Figure 2-3 Relation Between SP and Call Stack
SP is assigned to special function register (SFR) address 0F7H.
SP3
SP2
SP1
SP0
SP (0F7H)
(R)
bit 3
bit 2
bit 1
bit 0
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.
Summary of Contents for ML63326
Page 3: ......
Page 13: ......
Page 14: ...Chapter 1 Overview 1 ...
Page 15: ......
Page 37: ...1 22 ML63326 User s Manual Chapter 1 Overview ...
Page 38: ...Chapter 2 CPU and Memory Spaces 2 ...
Page 39: ......
Page 50: ...CPU Control Functions Chapter 3 3 ...
Page 51: ......
Page 57: ...3 6 ML63326 User s Manual Chapter 3 CPU Control Functions ...
Page 58: ...Interrupt INT326 Chapter 4 4 ...
Page 59: ......
Page 71: ...4 12 ML63326 User s Manual Chapter 4 Interrupt INT326 ...
Page 72: ...Clock Generator Circuit OSC Chapter 5 5 ...
Page 73: ......
Page 83: ...5 10 ML63326 User s Manual Chapter 5 Clock Generator Circuit OSC ...
Page 84: ...Time Base Counter TBC Chapter 6 6 ...
Page 85: ......
Page 90: ...Timers TIMER Chapter 7 7 ...
Page 91: ......
Page 115: ...7 24 ML63326 User s Manual Chapter 7 Timers TIMER ...
Page 116: ...Chapter 8 8 100 Hz Timer Counter 100HzTC ...
Page 117: ......
Page 121: ...8 4 ML63326 User s Manual Chapter 8 100 Hz Timer Counter 100HzTC ...
Page 122: ...Chapter 9 9 Watchdog Timer WDT ...
Page 123: ......
Page 128: ...Chapter 10 10 Ports INPUT OUTPUT I O PORT ...
Page 129: ......
Page 170: ...Chapter 11 11 External Memory Transfer Function EXTMEM ...
Page 171: ......
Page 179: ...11 8 ML63326 User s Manual Chapter 11 External Memory Transfer Function EXTMEM ...
Page 180: ...Chapter 12 12 Melody Driver MELODY63K ...
Page 181: ......
Page 195: ...12 14 ML63326 User s Manual Chapter 12 Melody Driver MELODY63K ...
Page 196: ...13 Chapter 13 Voice Synthesis ...
Page 197: ......
Page 228: ...14 Chapter 14 Shift Register SFT ...
Page 229: ......
Page 236: ...15 Chapter 15 LCD Driver LCD ...
Page 237: ......
Page 250: ...16 Chapter 16 Battery Low Detect Circuit BLD ...
Page 251: ......
Page 255: ...16 4 ML63326 User s Manual Chapter 16 Battery Low Detect Circuit BLD ...
Page 256: ...Chapter 17 17 Power Supply Circuit POWER ...
Page 257: ......
Page 260: ...Appendixes ...
Page 261: ......
Page 321: ...Appendix 60 ML63326 User s Manual Appendix G ...