Intel 8XC196MH CPU Special-function Registers SFRs, CPU SFRs, Address High Odd Byte Low Even Byte

MEMORY PARTITIONS

Your program must load a word-aligned (even) address into the stack pointer. Select an address that is two bytes greater than the desired starting address because the CPU automatically decre- ments the stack pointer before it pushes the first byte of the return address onto the stack. Remem- ber that the stack grows downward, so allow sufficient room for the maximum number of stack entries. The stack must be located in either the internal register file or external RAM. The stack can be used most efficiently when it is located in the register file.

The following example initializes the top of the upper register file (8XC196MC, MD) as the stack. (For the 8XC196MH, the immediate value would be #300H.)

LD SP, #200H ;Load stack pointer

The following example shows how to allow the linker locator to determine where the stack fits in the memory map that you specify.

LD SP, #STACK

4.1.6.3CPU Special-function Registers (SFRs)

Locations 0000–0017H in the lower register file are the CPU SFRs (Table 4-8). Appendix C de- scribes the CPU SFRs.

Table 4-8. CPU SFRs

Address	High (Odd) Byte	Low (Even) Byte
0016H	Reserved	Reserved
0014H	Reserved	WSR
0012H	INT_MASK1	INT_PEND1
0010H	Reserved	Reserved
000EH	Reserved	Reserved
000CH	Reserved	Reserved
000AH	Reserved	WATCHDOG
0008H	INT_PEND	INT_MASK
0006H	PTSSRV (H)	PTSSRV (L)
0004H	PTSSEL (H)	PTSSEL (L)
0002H	ONES_REG (H)	ONES_REG (L)
0000H	ZERO_REG (H)	ZERO_REG (L)

NOTE

Using any SFR as a base or index register for indirect or indexed operations can cause unpredictable results because external events can change the contents of SFRs. Also, because some SFRs are cleared when read, consider the implications of using an SFR as an operand in a read-modify-write instruction (e.g., XORB).

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