at43usb320a ATMEL Corporation, at43usb320a Datasheet - Page 10

• Manufacturer Part Number: at43usb320a
• Description: Full-speed Usb Microcontroller With An Embedded Hub
• Manufacturer: ATMEL Corporation

SRAM Data
Memory
10
AT43USB320A
Table 3 summarizes how the AT43USB320A 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-increment. 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 1024 bytes of internal data
SRAM in the AT43USB320A 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 and Table 4 give an
overview of these registers.
1443E–USB–4/04