Texas Instruments MSP50C614 manual String Instructions, Registers register# = value

Models: MSP50C614

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String Instructions

4.8 String Instructions

Class 1, 2, 3, and 6 instructions can have string modes. During the execution of string instruction, STR register value plus 2 is assumed as string length. An accumulator string is a group of consecutive accumulators spanning from An to the next N consecutive accumulators (N is the length of the string). The STR register should be loaded with N±2 to define a string length, N. A value of zero in the STR register defines a string length of 2 (string length 1 means the instruction is not in string mode). Arithmetic string instructions treat the string as an N word arithmetic value. The result is also an arithmetic value of the same length. Conditionals are set as they would be set without string mode. Comparing two strings is equivalent to comparing each bit of the string. The accumulator status is modified representing the outcome of the entire operation. Examine the following examples.

Table 4±43. Initial Processor State for String Instructions

Registers (register# = value)

AP0 = 2

AP1 = 21 (0x15)

AP2 = 11 (0x0B)

AP3 = 29 (0x1D)

 

 

 

 

 

 

AC0 =

AC1 =

 

AC2 =

AC3 =

 

 

 

 

 

 

 

AC4 =

AC5 =

 

AC6 =

AC7 =

 

 

 

 

 

 

AC8 =

AC9 =

 

AC10 =

AC11 = 0xAAAA

 

 

 

 

AC12 = 0xAAAA

AC13 = 0xAAAA

AC14 = 0xAAAA

AC15 = 0xAAAA

 

 

 

 

 

 

AC16 =

AC17 =

 

AC18 =

AC19 =

 

 

 

 

 

AC20 =

AC21 = 0x1223

AC22 = 0xFBCA

AC23 = 0x233E

 

 

 

 

 

data memory (*address = data)

 

 

 

 

 

 

 

 

 

 

*0x0200 = 0x12AC

*0x0201

= 0xEE34

*0x0202 = 0x9086

*0x0203

= 0xCDE5

 

 

 

 

program memory (*address = data)

 

 

 

 

 

 

 

 

 

*0x1400 = 0x0123

*0x1401

= 0x4567

*0x1402 = 0x89AB

*0x1403

= 0xCDEF

 

 

 

 

 

 

*0x1404 = 0xFEDC

*0x1405

= 0xBA98

*0x1404 = 0x7654

*0x1405

= 0x3210

 

 

 

 

 

Example 4.8.1

MOV STR, 4±2;

string length = 2

MOVS A0, 0x1400

Refer to initial the processor state in Table 4±43. A0 points to AC2. Consider a program memory location string of length 4 at 0x1400 = 0xCDEF89AB45670123. STR equal to 4±2=2, defines a string length of 4. Final result, AC2=0x0123, AC3=0x4567, AC4=0x89AB, and AC5=0xCDEF,

Example 4.8.2

MOV STR, 3±2;

string

length = 3

 

ADDS A1~, A1,

*0x0200

 

Refer to the initial processor state in Table 4±43. A1 is AC21, A1~ is AC5, the

Assembly Language Instructions

4-55

Page 147
Image 147
Texas Instruments MSP50C614 manual ±43. Initial Processor State for String Instructions, Registers register# = value