AT43USB325E-AC Atmel, AT43USB325E-AC Datasheet - Page 40

• Manufacturer Part Number: AT43USB325E-AC
• Description: IC USB KEYBOARD CTRLR HUB 64LQFP
• Manufacturer: Atmel
• Series: AVR®r

Specifications of AT43USB325E-AC

• Applications: Keyboard Controller
• Core Processor: AVR
• Program Memory Type: SRAM (16 kB)
• Controller Series: AT43USB
• Ram Size: 512 x 8
• Interface: SPI, 3-Wire Serial
• Number Of I /o: 42
• Voltage - Supply: 4.4 V ~ 5.25 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 64-LQFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

5. AVR Register Set
5.1
5.1.1
40
Status Register and Stack Pointer
AT43USB325
Status Register – SREG
• Bit 7 – I: Global Interrupt Enable
The global interrupt enable bit must be set (one) for the interrupts to be enabled. The individual
interrupt enable control is then performed in separate control registers. If the global interrupt
enable bit is cleared (zero), none of the interrupts are enabled independent of the individual
interrupt enable settings. The I-bit is cleared by the hardware after an interrupt has occurred,
and is set by the RETI instruction to enable subsequent interrupts.
• Bit 6 – T: Bit Copy Storage
The bit copy instructions BLD (Bit LoaD) and BST (Bit STore) use the T bit as source and desti-
nation 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.
• Bit 5 – H: Half Carry Flag
The half carry flag H indicates a half carry in some arithmetic operations. See the Instruction Set
Description for detailed information.
• 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 over-
flow flag V. See the Instruction Set Description for detailed information.
• Bit 3 – V: Two's Complement Overflow Flag
The two's complement overflow flag V supports two's complement arithmetics. See the Instruc-
tion Set Description for detailed information.
• Bit 2 – N: Negative Flag
The negative flag N indicates a negative result after the different arithmetic and logic operations.
See the Instruction Set Description for detailed information.
• Bit 1 – Z: Zero Flag
The zero flag Z indicates a zero result after the different arithmetic and logic operations. See the
Instruction Set Description for detailed information.
• Bit 0 – C: Carry Flag
The carry flag C indicates a carry in an arithmetic or logic operation. See the Instruction Set
Description for detailed information.
Note that the status register is not automatically stored when entering an interrupt routine and
restored when returning from an interrupt routine. This must be handled by software.
Read/Write
Initial Value
$3F ($5F)
Bit
R/W
7
0
I
R/W
6
T
0
R/W
H
5
0
R/W
S
4
0
R/W
V
3
0
R/W
N
2
0
R/W
Z
1
0
R/W
C
0
0
3355C–USB–4/05
SREG