DMC73C167 datasheet(18/90 Pages) DAEWOO

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8Bit Single Chip Microcontroller

DMC73C167

4.4 Stack Pointer (SP)

The stack pointer(SP) is an 8-bit register in the CPU which is typically used to hold a pointer

in RAM (the register file). However, the SP can also be used as temporary data storage if a

stack is not implemented, or if the SP contents are not needed.

When a stack is implemented, the SP points to the last or top entry on the stack. The SP

is automatically incremented just before data is pushed onto the stack and automatically

decremented immediately after data is popped from the stack. Upon assertion of the

RESET function (see Section 4.8) 01h is loaded into the SP. The size of the stack can be

changed from the 255-level stack at RESET to a smaller stack by execuiting a stack

initialization program as illustrated in Figure 4-3. This feature allows the stack to be located

anywhere in the register file. The SP is initialized through the B register (R1).

Figure 4-3. Example of Stack Initialization in the Register File

4.5 Status Register (ST)

The status register(ST) is an 8-bit register in the CPU that contains three conditional status

bits : carry(C), sign(N), and zero(Z). It also contains a global interrupt enable bit(I) as shown

in Figure 4-4 below.

Figure 4-4. Status Register (ST)

Bit

Con

Future use

C = carry out, N=sign, Z = zero, I = Interrupt enable

0001h

0002h

0003h

0004h

0005h

0006h

01h

PCH

PCL

04h

PCH

PCL

06h

Interrupt

Call

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