ATTINY43U View Datasheet(PDF) - Atmel Corporation
Part Name
Description
Manufacturer
ATTINY43U
Atmel Corporation
ATTINY43U Datasheet PDF : 210 Pages
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ATtiny43U
Figure 4-3. The X-, Y-, and Z-registers
15
XH
XL
0
X-register
7
07
0
R27 (0x1B)
R26 (0x1A)
15
YH
YL
0
Y-register
7
07
0
R29 (0x1D)
R28 (0x1C)
Z-register
15
ZH
7
0
R31 (0x1F)
ZL
0
7
0
R30 (0x1E)
In the different addressing modes these address registers have functions as fixed displacement,
automatic increment, and automatic decrement (see the instruction set reference for details).
4.6 Stack Pointer
The Stack is mainly used for storing temporary data, local variables and return addresses for
interrupts and subroutine calls. The Stack Pointer Register always points to the top of the Stack,
in the data SRAM Stack area where the subroutine and interrupt stacks are located.
The Stack in the data SRAM must be defined by the program before any subroutine calls are
executed or interrupts are enabled. The Stack Pointer must be set to point above start of the
SRAM (see Figure 5-2 on page 16). The initial Stack Pointer value equals the last address of the
internal SRAM.
Note that the Stack is implemented as growing from higher to lower memory locations. This
means a Stack PUSH command decreases the Stack Pointer. See Table 4-1.
Table 4-1. Stack Pointer instructions
Instruction Stack pointer
PUSH
Decremented by 1
CALL
ICALL
RCALL
Decremented by 2
POP
Incremented by 1
RET
RETI
Incremented by 2
Description
Data is pushed onto the stack
Return address is pushed onto the stack with a
subroutine call or interrupt
Data is popped from the stack
Return address is popped from the stack with return
from subroutine or return from interrupt
The AVR Stack Pointer is implemented as two 8-bit registers in the I/O space. The number of
bits actually used is implementation dependent.
Note that the data space in some implementations of the AVR architecture is so small that only
SPL is needed. In this case, the SPH Register will not be present.
11
8048C–AVR–02/12
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