EM78P259N/260N
8-Bit Microprocessor with OTP ROM
6
Function Description
6.1
Operational Registers
6.1.1 R0 (Indirect Address Register)
R0 is not a physically implemented register. Its major function is to perform as an
indirect address pointer. Any instruction using R0 as a pointer, actually accesses the
data pointed by the RAM Select Register (R4).
6.1.2 R1 (Time Clock /Counter)
Increased by an external signal edge which is defined by the TE bit (CONT-4)
through the TCC pin, or by the instruction cycle clock.
Writable and readable as any other registers
The TCC prescaler counter (IOCC1) is assigned to TCC
The contents of the IOCC1 register is cleared whenever –
•
a value is written to TCC register.
•
a value is written to TCC prescaler bits (Bit3, 2, 1, 0 of the CONT register)
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during power on reset, /RESET, or WDT time out reset.
6.1.3 R2 (Program Counter) and Stack
R3
Reset Vector
Hardware Interrupt Vector
A10
A9 A8
A7
CALL
RET
RETL
RETI
~
A0
000H
003H
~
01EH
User Memory
Space
00 PAGE0 0000~03FF
01 PAGE1 0400~07FF
Stack Level 1
Stack Level 2
Stack Level 3
Stack Level 4
Stack Level 5
Stack Level 6
Stack Level 7
Stack Level 8
On-chip Program
Memory
3FEH
7FFH
Fig. 5-2 Program Counter Organization
R2 and hardware stacks are 12-bit wide. The structure is depicted in the table
under Section 6.1.3.1,
Data Memory Configuration
(next page).
Generates 2K×13 bits on-chip ROM addresses to the relative programming
instruction codes. One program page is 1024 words long.
The contents of R2 are all set to "0"s when a RESET condition occurs.
6
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Product Specification (V1.0) 06.16.2005
(This specification is subject to change without further notice)
EMC [ ELAN MICROELECTRONICS CORP ]
