em78p468n ELAN Microelectronics Corp, em78p468n Datasheet - Page 12

• Manufacturer Part Number: em78p468n
• Description: 8-bit Microcontroller
• Manufacturer: ELAN Microelectronics Corp

EM78P468N/L
8-Bit Microcontroller
6 Function Description
6 •
6.1 Operational Registers
6.1.1 R0/IAR (Indirect Addressing 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 register, actually accesses the
data pointed by the RAM Select Register (R4).
6.1.2 R1/TCC (Timer Clock Counter)
The Timer Clock Counter is incremented by an external signal edge applied to TCC, or
by the instruction cycle clock. It is written and read by the program as any other
register.
6.1.3 R2/PC (Program Counter)
The structure of R2 is depicted in Fig. 6-1, Program Counter Organization.
The configuration structure generates 4K×13 bits on-chip ROM addresses to the
The contents of R2 are all set to "0"s when a Reset condition occurs.
"JMP" instruction allows direct loading of the lower 10 program counter bits. Thus,
"CALL" instruction loads the lower 10 bits of the PC, and then PC+1 is pushed onto
"RET" ("RETL k", "RETI") instruction loads the program counter with the contents
"ADD R2, A" allows a relative address to be added to the current PC, and the ninth
"MOV R2, A" allows loading of an address from the "A" register to the lower 8 bits of
The most significant bits (A10~A11) will be loaded with the content of PS0~PS1 in
relative programming instruction codes.
"JMP" allows the PC to jump to any location within a page.
the stack. Thus, the subroutine entry address can be located anywhere within a
page.
at the top of the stack.
and above bits of the PC will increase progressively.
the PC, and the ninth and tenth bits (A8 ~ A9) of the PC will remain unchanged.
the Status register (R3) upon execution of a "JMP" or "CALL" instruction.
(Address: 00h)
(Address: 01h)
(Address: 02h)
(This specification is subject to change without further notice)
Product Specification (V1.6) 12.31.2007