EM78P153EN EMC [ELAN Microelectronics Corp], EM78P153EN Datasheet - Page 7

• Manufacturer Part Number: EM78P153EN
• Description: EM78P153E is an 8-bit microprocessor with low-power and high-speed CMOS technology
• Manufacturer: EMC [ELAN Microelectronics Corp]

This specification is subject to change without prior notice.
3. R2 (Program Counter) & Stack
• Depending on the device type, R2 and hardware stack are 9-bit wide. The structure is depicted in
• 512 13 bits on-chip OTP ROM addresses to the relative p rogramming instruction codes. One
• R2 is set as all "0"s when under RESET condition.
• "JMP" instruction allows direct loading of the lower 9 program counter bits. Thus, "JMP" allows PC to
• "CALL" instruction loads the lower 9 bits of the PC, and then PC+1 is pushed into the stack. Thus,
• "RET" ("RETL k", "RETI") instruction loads the program counter with the contents of the top-level
• "ADD R2,A" allows the contents of ‘A’ to be added to the current PC, and the ninth of the PC are
• "MOV R2,A" allows to load an address from the "A" register to the lower 8 bits of the PC, and the
• Any instruction that is written to R2 (e.g. "ADD R2,A", "MOV R2,A", "BC R2,6",
• All instructions are single instruction cycle (fclk/2 or fclk/4), except for the instruction that would
Fig.3.
program page is 512 words long.
go to any location within a page.
the subroutine entry address can be located anywhere within a page.
stack.
cleared.
ninth bits of the PC are cleared.
ninth bits (A8) of the PC to be cleared. Thus, the computed jump is limited to the first 256 locations
of a page.
change the contents of R2. This instruction will need one more instruction cycle.
PC
0 0
00
A8
Fig. 3 Program Counter Organization
1FF
000
Page 0
A7
~
7
A0
CALL
RET
RETL
RETL K
EM78P153E
Stack 1
Stack 2
Stack 3
Stack 4
Stack 5
) will cause the
OTP ROM
2002/03/01