Aug.2007

www.eorex.com

Memory

The EU101x has a 14-bit program counter which can totally address 16K x 8 bits. All the special function

registers, data RAM, stack RAM and program ROM are assigned in this area as the following diagram.

0000H

Special Function Register

0022H

Un-used

00A0H

( zero page )

Data RAM : 96 x 8 bits

00FFH

0100H

Data & Stack RAM : 32 x 8 bits

011FH

Un-used

3FFFH

Figure_A

Memory mapping diagram

Program ROM

The EU101x contains 4Kx8 bit program OTP and its addressing size is assigned from $3000H to

$3FFFH. After power on reset, the data restored in addresses $3FFCH and $3FFDH are loaded into

program counter. It means that RESET vector address is located in $3FFCH and $3FFDH.

Data RAM and STACK RAM

The EU101x data RAM are located from $A0H to $11FH. All the data RAM area from $A0H to $0FFH

could be accessed by zero-page addressing mode. That STACK RAM could be accessed from $100H to

$11FH. Actually, the area of $100H ~ $11FH, could be accessed as data RAM or STACK RAM. User

needs to preset stack pointer (SP) after power on reset. Program Counter (PC) should be initialized after

power on reset that ROM address $3FFCH and $3FFDH content will be loaded into Program Counter.

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