Fujitsu F2MC-8FX manual Example of Saving Data in Stack Area

CHAPTER 2 MEMORY SPACE

Figure 2.2-3 Example of Saving Data in Stack Area

Before execution		MEMORY				After execution		MEMORY
					PUSHW A
SP	1235H		67H	1235H		SP	1233H		67H	1235H
				1234H						1234H
A						A			CDH
	ABCDH						ABCDH
				1233H				ABH	1233H
				1232H						1232H

Figure 2.2-4 Example of Returning Data from Stack Area

Before execution

SP	5678H
IX	XXXXH

MEMORY				After execution
			POPW IX
		567BH		SP	567AH
		567AH
				IX	FEDCH
		5679H
	DCH
		5678H
	FEH

MEMORY

	567BH
	567AH
	5679H
DCH
	5678H
FEH

■Direct Area

The direct area in the F2MC-8FX CPU is located at the lower side of the memory space or the 1152 bytes from 0000H to 047FH and is mainly accessed by direct addressing and bit direct addressing. The area that can be used at a time by direct addressing and bit direct addressing is 256 bytes. 128 bytes of 0000H to 007FH can be used at any time as a direct area. 0080H to 047FH is a direct bank of 128 bytes ⋅ 8 and can use one direct bank as a direct area by setting the direct bank pointer (DP). Conversion from the operand address of direct addressing and bit direct addressing to the real address is done by the conversion rule shown in Table 2.2-1by using DP.

Access to it is obtained by the 2-byte instruction.

The I/O control registers and part of RAM that are frequently accessed are arranged in this direct area.

Table 2.2-1 Conversion Rule for Actual Address of Direct Addressing and Bit Direct Addressing

Operand address	Direct bank pointer (DP)	Actual address
00H to 7FH		0000H to 007FH
	000	0080H to 00FFH
	001	0100H to 017FH
	010	0180H to 01FFH
80H to FFH	011	0200H to 027FH
	100	0280H to 02FFH
	101	0300H to 037FH
	110	0380H to 03FFH
	111	0400H to 047FH

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