Question

CONFIDENTIAL BEE4323 1718H/SETA 3. If the content of memories ($3010) 77 A1 B2 C3 3D 4F 44 55, obtain the new contents of memories when the following program is executed. LDX #$3010 BRSET 1,X 07, SCAN BSET 3.x $45 BCLR 4,X SB3 BRA EXIT BSET 5,X $66 BCLR 6,X SBB BRA EXIT SCAN EXIT (S3010) 16 points ICO2, PO2, C4]

Answer 1

ANSWER:

Instructions:

LDX: load value stored at given address

BRSET: Branch to given label if given mask bits are set in the operand

BSET: set bits in the operand given by the mask BCLR: clear bits in the operand given by the mask BRA: Branch always

When given sequence of instructions executed: LDX #S3010 // load base address of the given array

BRSET 1,X 07, SCAN // Check if first three LSBs(07 — 00000111) are set in X+1 i.e. B2, false BSET 3,X $45 // set bits in X+3(C311000011) given mask 01110110

01110110

11000011

01110110 => x+3 becomes 36                         00111010

BCLR 4, X $B3 // clear bits B3(10110011)

01100111 => xi-3 becomes 15                                     00011001

BCLR 4, X$B3 // clear bits B3(11000100)

00110011

11000100

00110011 => no change, all the bits in the mask are already 0 BRA EXIT // jump to exit

(S3010): 77 A1 B2 15 3D 4F 44 55