Texas Instruments MSP50C614 ±4. Data Memory Example, Which uses the absolute word memory address

Bit, Byte, Word and String Addressing

Figure 4±4. Data Memory Example

Absolute Word	Data Memory Location (even) = 2 *		MS Byte	LS Byte	Data Memory
Memory Location	(Absolute word memory location)				Location (odd)
0x0000	0x0000		0x12	0x34	0x0001
0x0001	0x0002		0x56	0x78	0x0003
0x0002	0x0004		0x9a	0xbc	0x0005
0x0003	0x0006		0xde	0xf0	0x0007
0x0004	0x0008		0x11	0x22	0x0009
0x0005	0x000a		0x33	0x44	0x000b
	Example 4.5.4	MOV STR, 4±2
		MOV AP0, 2

MOVBS A0, *0x0003

Refer to Figure 4±4 for this example. The byte-string length is 4. It is loaded to the string register (STR) in the first instruction. AP0 is 2 and it points to AC2. Third instruction loads the value of the string at byte address, 0x0003, and subsequently stores its contents into four consecutive accumulators starting from AC2. The result is, AC2 = 0x0078, AC3 = 0x009A, AC4 = 0x00BC, AC5 = 0x00DE.

Example 4.5.5	MOV	STR,	4±2
	MOV	AP0,	2
	MOVS A0,		*0x0003

Refer to Figure 4±4 for this example. The byte-string length is 4. AP0 is loaded with 2 and points to AC2. The third instruction loads the value of the string at address 0x0002 (LSB bit is assumed 0) and stored into four consecutive accumulators starting from AC2. The result is, AC2 = 0x5678, AC3 = 0x9ABC, AC4 = 0xDEF0, AC5 = 0x1122. Same result can be obtained by replacing the third instruction by,

MOVS A0, *0x0001 * 2

which uses the absolute word memory address.

Example 4.5.6	MOV STR, 4±2
	OV AP0,	2
	MOV R0,	0x0005

MOVBS A0, *R0++

Refer to Figure 4±4 for this example. The byte string length is 4. AP0 points to AC2. R0 is loaded with 0x0005. The fourth instruction loads the value of the byte-string at the address in R0 (i.e, 0x0005 in byte mode). R0 auto±incre- ments by 1 after every fetch and stores the RAM contents into four consecutive accumulators starting from AC2. The result is, AC2 = 0x00BC, AC3 = 0x00DE, AC4 = 0x00F0, AC5 = 0x0011. There were four byte fetches and the new value of R0 = 0x0009.

Assembly Language Instructions 4-47