em78p809n ELAN Microelectronics Corp, em78p809n Datasheet - Page 11

• Manufacturer Part Number: em78p809n
• Description: 8-bit Microcontroller
• Manufacturer: ELAN Microelectronics Corp

Product Specification (V1.0) 07.26.2005
(This specification is subject to change without further notice)
R0 is not a physically implemented register. Its major function is to act as an indirect
addressing pointer. Any instruction using R0 as a pointer actually accesses data
pointed by the RAM Select Register (R4).
This register is writable and readable just like the other registers. The contents of the
prescaler counter are cleared only when a value is written into the TCC register.
R0/IAR − Indirect Addressing Register ( Address: 00h )
R1/TCC − Time Clock /Counter ( Address: 01h )
R2/PC − Program Counter & Stack ( Address: 02h )
structure is depicted in Fig.4.
programming instruction codes. One program page is 1024 words long.
Thus, "JMP" allows the PC to go to any location within a page.
pushed into the stack. Thus, the subroutine entry address can be located
anywhere within a page.
contents of the top-level stack.
instruction that would change the contents of R2. Such instruction will need
one more instruction cycle.
vector at Page 0. The CPU will store ACC, R3 status and R5 PAGE
automatically, it will restore after instruction RETI.
Depending on the device type, R2 and hardware stack are 10-bit wide. The
Generates 8192 ×13 bits on-chip OTP ROM addresses to the relative
R2 is set as all "0"s when under RESET condition
"JMP" instruction allows direct loading of the lower 10 program counter bits.
"CALL" instruction loads the lower 10 bits of the PC, and then PC+1 is
"RET" ("RETL k", "RETI") instruction loads the program counter with the
All instructions are single instruction cycle (fclk/2 or fclk/4) except for the
For an interrupt trigger, the program ROM will jump to individual interrupt
8-Bit Microcontroller
EM78P809N
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