8085 program to show masking of lower and higher nibbles of 8-bit number

In this program we will see how to lower and upper nibbles are masked in 8085.

Problem Statement

Write 8085 Assembly language program to mask the upper and lower nibble of an 8-bit number. The number is stored at location 8000H. Lower and Upper nibbles will be stored at location 8001H and 8002H.

Discussion

The masking is basically ANDing two numbers. When we want to mask the upper nibble of an 8-bit number say 2D (0010 1101), then we will AND with 0F (0000 1111), so we will get 0D (0000 1101). By masking with F0 (1111 0000), the result will be 20 (0010 0000). Now by shifting the upper nibble, we will get 02 (0000 0010).

Input

Address	Data
…	…
8000	AB

Flow Diagram

Program

Address	HEX Codes	Mnemonics	Comments
F000	21, 00, 80	LXI H,8000H	Initialize HL pair to get number
F003	7E	MOV A,M	Take the number from memory to accumulator
F004	47	MOV B,A	Store A to B
F005	E6, 0F	ANI 0FH	Get the lower nibble by masking upper one.
F007	23	INX H	Point to next location
F008	77	MOV M,A	Store Lower nibble to memory
F009	78	MOV A,B	Take the number from B to A
F00A	E6, F0	ANI F0H	Take the upper nibble by masking lower one.
F00C	0F	RRC	Rotate acc four times
F00D	0F	RRC
F00E	0F	RRC
F00F	0F	RRC
F010	23	INX H	Point to next location
F011	77	MOV M,A	Store the upper nibble to memory
F012	76	HLT	Terminate the program