AT43USB355M-AC ATMEL [ATMEL Corporation], AT43USB355M-AC Datasheet - Page 11

• Manufacturer Part Number: AT43USB355M-AC
• Description: Full-speed USB Microcontroller with Embedded Hub, ADC and PWM
• Manufacturer: ATMEL [ATMEL Corporation]

SRAM Data
Memory
2603G–USB–04/06
Figure 5. READ Timing
Table 3 summarizes how the AT43USB355 SRAM Memory is organized. The lower 1120 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 1024 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 reg-
isters. 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 AT43USB355 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.
MOSI
MISO
SSN
SCK
0
INSTRUCTION
1
2
HIGH IMPEDANCE
3
4
5
6
7
15
8
14
BYTE ADDRESS
9 10 11 20 21 22 23 24 25 26 27 28 29 30
13
...
3
2
1
0
MSB
7
6
5
DATA OUT
AT43USB355
4
3
2
1
0
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