Question

Consider the following assembly code segment below: LDR R0, = 0x40004C00 ADD R0, #0x21 MOV R1, #0x0F STRB R1, [R0, #0x04] MOV R1, #0x?? STRB R1, [R0, #0x06] STRB R1, [R0, #0x02]

1. What port is being configured in this assembly code segment?
2. What byte should you move to R1 in order to assign all of the input pins as pull-ups while keeping the output pins as LOW? (at the place #0x??)

Answer 1

The assembly code segment is configuring a port and the byte to move to R1 in order to assign all input pins as pull-ups while keeping the output pins as LOW is 0xFF.

Step-by-step explanation:

Answer:

1. The assembly code segment is configuring a port.
2. The byte to move to R1 in order to assign all of the input pins as pull-ups while keeping the output pins as LOW is 0xFF.

Step-by-step explanation:

In the given assembly code segment, the instruction LDR R0, = 0x40004C00 loads the base address of the port into R0. The instruction ADD R0, #0x21 adds an offset of 0x21 to the base address, pointing to a specific register in the port. The instruction MOV R1, #0x0F moves the value 0x0F (LOW) to R1. The instruction STRB R1, [R0, #0x04] stores the value of R1 at an offset of 0x04 from the address in R0, which configures a specific pin in the port as LOW. To assign all input pins as pull-ups while keeping the output pins as LOW, the byte 0xFF (11111111 in binary) needs to be moved to R1. This will set all the input pins as pull-ups and the output pins as LOW. The instruction STRB R1, [R0, #0x06] stores the value of R1 at an offset of 0x06 from the address in R0, which configures the pins accordingly.