Samsung S3F80JB manual Working Registers, Byte Working Register Areas Slices

S3F80JB ADDRESS SPACES

WORKING REGISTERS

Instructions can access specific 8-bit registers or 16-bit register pairs using either 4-bit or 8-bit address fields. When 4-bit working register addressing is used, the 256-byte register file can be seen by the programmer as consisting of 32 8-byte register groups or "slices." Each slice consists of eight 8-bit registers.

Using the two 8-bit register pointers, RP1 and RP0, two working register slices can be selected at any one time to form a 16-byte working register block. Using the register pointers, you can move this 16-byte register block anywhere in the addressable register file, except for the set 2 area.

The terms slice and block are used in this manual to help you visualize the size and relative locations of selected working register spaces:

—One working register slice is 8 bytes (eight 8-bit working registers; R0–R7 or R8–R15)

—One working register block is 16 bytes (sixteen 8-bit working registers; R0–R15)

All of the registers in an 8-byte working register slice have the same binary value for their five most significant address bits. This makes it possible for each register pointer to point to one of the 24 slices in the register file. The base addresses for the two selected 8-byte register slices are contained in register pointers RP0 and RP1.

After a reset, RP0 and RP1 always point to the 16-byte common area in set 1 (C0H–CFH).

		Slice 32		FFH
				F8H
				F7H
	1 1 1 1 1 X X X			F0H
	RP1 (Registers R8-R15)
Each register pointer points to				CFH
one 8-byte slice of the register
				C0H
space, selecting a total 16-byte
working register block.
~			~
	0 0 0 0 0 X X X			10H
	RP0 (Registers R0-R7)			0FH
				08H
		Slice 1
				07H
				00H

Set 1 Only

Figure 2-6. 8-Byte Working Register Areas (Slices)

2-10