Final answer:
The ZLPM macro is defined for initialising the Z pointer for the LPM instruction. It sets the lower part of the address into r30 and clears r31, preparing it to access CSEG data.
Step-by-step explanation:
To create a macro that initialises the Z pointer for use by the LPM (Load Program Memory) instruction in an assembly language for AVR microcontrollers, you need to set up the Z register with the address of the CSEG (code segment) data. Below is an example of how you might write this macro called ZLPM:
#define ZLPM(TABLE_ADDR) \
"ldr r30, =TABLE_ADDR\\\t" \
"clr r31\\"
This macro takes an argument TABLE_ADDR, which is the address of the table. The macro uses an assembly command to load the lower 8 bits of the address into r30 (the low byte of the Z register) and clears r31 (the high byte of the Z register), assuming that we are accessing the CSEG which starts at address 0x0000.
To use the ZLPM macro, you would simply write:
ZLPM(DATATBL)
Where DATATBL is the label or address of the data table in the code segment.
The complete question is: Assume that we have a table in CSEG and we wish to access the table via the LPM instruction. Before using LPM, the Z pointer must be initialized. Write a macro that initialises the Z pointer for use by the LPM instruction. The macro is called ZLPM and it has one argument. The argument is the address of the table in CSEG. An example of how the macro can be used: ZLPM DATATBL Where DATATBL is the label/address of the is: