AT43USB325E-AC Atmel, AT43USB325E-AC Datasheet - Page 12

• 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

3.5
SRAM Data Memory
Table 3-3
summarizes how the AT43USB325 SRAM Memory is organized. The lower 608 Data
Memory locations address the Register file, the I/O Memory and the internal data SRAM. The
first 96 locations address the Register File + I/O Memory, and the next 512 locations address the
internal data SRAM. The five different addressing modes for the data memory cover: Direct,
Indirect with Displacement, Indirect, Indirect with Pre-decrement and Indirect with Post-incre-
ment. In the register file, registers R26 to R31 feature the indirect addressing pointer registers.
Direct addressing reaches the entire data space.
The Indirect with Displacement mode features 63 address locations that reach from the base
address given by the Y- or Z-register.
When using register indirect addressing modes with automatic pre-decrement and post-incre-
ment, the address registers X, Y, and Z are decremented and incremented.
The 32 general-purpose working registers, 64 I/O registers and the 512 bytes of internal data
SRAM in the AT43USB325 are all accessible through these addressing modes.
To manage the USB hardware, a special set of registers is assigned. These registers are
mapped to SRAM space between addresses $1F00 and 1FFF.
Table 3-3
and
Table 3-4
give an
overview of these registers.
AT43USB325
12
3355C–USB–4/05