AT90SCR100 datasheet(29/433 Pages) ATMEL

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TPR0327AY–SMS–30Jan09

AT90SCR100

6.4

I/O Memory

The I/O space definition of the AT90SCR100 is shown in “Register Summary” on page 417.

All AT90SCR100 I/Os and peripherals are placed in the I/O space. All I/O locations may be

accessed by the LD/LDS/LDD and ST/STS/STD instructions, transferring data between the 32

general purpose working registers and the I/O space. I/O Registers within the address range

0x00 - 0x1F are directly bit-accessible using the SBI and CBI instructions. In these registers, the

value of single bits can be checked by using the SBIS and SBIC instructions. Refer to the

instruction set section for more details. When using the I/O specific commands IN and OUT, I/O

addresses 0x00 - 0x3F must be used. When addressing I/O Registers as data space using LD

and ST instructions, 0x20 must be added to these addresses. The AT90SCR100 is a complex

microcontroller with more peripheral units than can be supported within the 64 location reserved

in the Opcode of the IN and OUT instructions. For the Extended I/O space from 0x60 - 0xFF in

SRAM, only the ST/STS/STD and LD/LDS/LDD instructions can be used.

For compatibility with future devices, reserved bits should be written to zero if accessed.

Reserved I/O memory addresses should never be written.

Some of the Status Flags are cleared by writing a logical one to them. Note that, unlike most

other AVRs, the CBI and SBI instructions will only operate on the specified bit, and can therefore

be used on registers containing such Status Flags. The CBI and SBI instructions work with reg-

isters 0x00 to 0x1F only.

The I/O and peripherals control registers are explained in later sections.

6.4.1

General Purpose I/O Registers

The AT90SCR100 contains three General Purpose I/O Registers. These registers can be used

for storing any information, and they are particularly useful for storing global variables and Sta-

tus Flags. General Purpose I/O Registers within the address range 0x00 - 0x1F are directly bit-

accessible using the SBI, CBI, SBIS, and SBIC instructions.

6.4.2

GPIOR2 – General Purpose I/O Register 2

6.4.3

GPIOR1 – General Purpose I/O Register 1

Bit

7654

0x2B (0x4B)

GPIOR2 [7..0]

GPIOR2

Read/write

R/W

Initial value

0000

0x00

Bit

7654

0x2A (0x4A)

GPIOR1 [7..0]

GPIOR1

Read/write

R/W

Initial value

0000

0x00

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