ATTINY20-EK1 Ver la hoja de datos (PDF) - Atmel Corporation
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ATTINY20-EK1 Datasheet PDF : 219 Pages
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4.8.3 SREG – Status Register
Bit
0x3F
Read/Write
Initial Value
7
6
5
4
3
2
1
0
I
T
H
S
V
N
Z
C
SREG
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0
0
0
0
0
0
0
0
z Bit 7 – I: Global Interrupt Enable
The Global Interrupt Enable bit must be set for the interrupts to be enabled. The individual interrupt enable control is then
performed in separate control registers. If the Global Interrupt Enable Register is cleared, none of the interrupts are
enabled independent of the individual interrupt enable settings. The I-bit is cleared by hardware after an interrupt has
occurred, and is set by the RETI instruction to enable subsequent interrupts. The I-bit can also be set and cleared by the
application with the SEI and CLI instructions, as described in the document “AVR Instruction Set” and “Instruction Set
Summary” on page 205.
z Bit 6 – T: Bit Copy Storage
The Bit Copy instructions BLD (Bit LoaD) and BST (Bit STore) use the T-bit as source or destination for the operated bit.
A bit from a register in the Register File can be copied into T by the BST instruction, and a bit in T can be copied into a bit
in a register in the Register File by the BLD instruction.
z Bit 5 – H: Half Carry Flag
The Half Carry Flag H indicates a Half Carry in some arithmetic operations. Half Carry is useful in BCD arithmetic. See
document “AVR Instruction Set” and section “Instruction Set Summary” on page 205 for detailed information.
z Bit 4 – S: Sign Bit, S = N ⊕ V
The S-bit is always an exclusive or between the Negative Flag N and the Two’s Complement Overflow Flag V. See
document “AVR Instruction Set” and section “Instruction Set Summary” on page 205 for detailed information.
z Bit 3 – V: Two’s Complement Overflow Flag
The Two’s Complement Overflow Flag V supports two’s complement arithmetic. See document “AVR Instruction Set”
and section “Instruction Set Summary” on page 205 for detailed information.
z Bit 2 – N: Negative Flag
The Negative Flag N indicates a negative result in an arithmetic or logic operation. See document “AVR Instruction Set”
and section “Instruction Set Summary” on page 205 for detailed information.
z Bit 1 – Z: Zero Flag
The Zero Flag Z indicates a zero result in an arithmetic or logic operation. See document “AVR Instruction Set” and
section “Instruction Set Summary” on page 205 for detailed information.
z Bit 0 – C: Carry Flag
The Carry Flag C indicates a carry in an arithmetic or logic operation. See document “AVR Instruction Set” and section
“Instruction Set Summary” on page 205 for detailed information.
ATtiny20 [DATASHEET] 14
Atmel-8235F-AVR-ATtiny20-Datasheet_09/2014
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