em78f644nso28s ELAN Microelectronics Corp, em78f644nso28s Datasheet - Page 59

• Manufacturer Part Number: em78f644nso28s
• Description: Flash Series 8-bit Microcontroller
• Manufacturer: ELAN Microelectronics Corp

Product Specification (V1.0) 05.05.2010
(This specification is subject to change without further notice)
Bit 4 (SBS0): Special register bank select bit. It is used to select Bank 0/1 of special
Bit 0 (GBS0): General register bank select bit. It is used to select Bank 0/1of general
6.3 Operational Registers for EM78F648/548N
6.3.1 R0: IAR (Indirect Addressing Register)
R0 is not a physically implemented register. Its major function is to perform as an
indirect addressing pointer. Any instruction using R0 as a pointer actually accesses
data pointed by the RAM Select Register (R4).
6.3.2 R1: BSR (Bank Selection Control Register)
Bits 7 ~ 5:
Bits 3~1:
6.3.3 R2: PC (Program Counter)
Bit 7
Depending on the device type, R2 and hardware stack are 12-bits wide. The
program counter structure is depicted in Figure 6-6 below.
Generates 8K×15 bits on-chip Flash ROM addresses to the relative programming
instruction codes. One program page is 4096 words long.
R2 is set as all "0"s when under RESET condition.
"JMP" instruction allows direct loading of the lower 12 program counter bits.
Thus, "JMP" allows PC to go to any location within a page.
"CALL" instruction loads the lower 12 bits of the PC, and the present PC value
will add 1 and is pushed into the stack. Thus, the subroutine entry address can
be located anywhere within a page.
"LJMP" instruction allows direct loading of the lower 13 program counter bits.
Therefore, "LJMP" allows PC to jump to any location within 8K (213).
"LCALL" instruction loads the lower 13 bits of the PC, and then PC+1 is pushed
into the stack. Thus, the subroutine entry address can be located anywhere
within 8K (213).
"RET" ("RETL k", "RETI") instruction loads the program counter with the contents
of the top-level stack.
0
Not used, set to “0” all the time.
0: Bank 0
1: Bank 1
Not used, set to “0” all the time.
0: Bank 0
1: Bank 1
register R5~R4F.
Bit 6
register R80~RFF.
0
Bit 5
0
EM78F648/644/642/641/548/544/542/541N
SBS0
Bit 4
Bit 3
0
Bit 2
0
8-Bit Microcontroller
Bit 1
0
GBS0
Bit 0
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