Texas-instruments MSP50C6xx Manuel d'utilisateur télécharger pdf (Page 141)

String Instructions

4-55Assembly Language 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

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

1 2 ... 136 137 138 139 140 141 142 143 144 145 146 ... 389 390

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Texas-instruments MSP50C6xx Manuel d'utilisateur Page 141