HT48CA0-2 Holtek Semiconductor, HT48CA0-2 Datasheet - Page 4

• Manufacturer Part Number: HT48CA0-2
• Description: (HT48RA0-2 / HT48CA0-2) Remote Type 8-Bit MCU
• Manufacturer: Holtek Semiconductor

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Program Counter - PC
The 10-bit program counter (PC) controls the sequence
in which the instructions stored in program ROM are ex-
ecuted and its contents specify a maximum of 1024 ad-
dresses.
After accessing a program memory word to fetch an in-
struction code, the contents of the program counter are
incremented by one. The program counter then points to
the memory word containing the next instruction code.
When executing a jump instruction, conditional skip ex-
ecution, loading PCL register, subroutine call, initial re-
set or return from subroutine, the PC manipulates the
program transfer by loading the address corresponding
to each instruction.
The conditional skip is activated by instruction. Once the
condition is met, the next instruction, fetched during the
current instruction execution, is discarded and a dummy
cycle replaces it to get the proper instruction. Otherwise
proceed with the next instruction.
The lower byte of the program counter (PCL) is a read-
able and writeable register (06H). Moving data into the
PCL performs a short jump. The destination will be
within 256 locations.
When a control transfer takes place, an additional
dummy cycle is required.
Program Memory - ROM
The program memory is used to store the program in-
structions which are to be executed. It also contains
Note:
Note:
Rev. 1.50
Initial reset
Skip
Loading PCL
Jump, call branch
Return from subroutine
TABRDC [m]
TABRDL [m]
Instruction(s)
*9~*0: Program counter bits
#9~#0: Instruction code bits
*9~*0: Table location bits
P9~P8: Current program counter bits
Mode
P9
*9
#9
S9
*9
*9
1
0
P8
*8
S8
#8
1
*8
*8
0
@7
@7
@7
*7
S7
#7
*7
Program Counter
0
Table Location
@6
@6
@6
*6
#6
S6
*6
4
0
data and table and is organized into 1024 14 bits, ad-
dressed by the program counter and table pointer.
Certain locations in the program memory are reserved
for special usage:
S9~S0: Stack register bits
@7~@0: PCL bits
@7~@0: Table pointer bits
Program Counter
Location 000H
This area is reserved for the initialization program. Af-
ter chip reset, the program always begins execution at
location 000H.
Table location
Any location in the EPROM space can be used as
look-up tables. The instructions TABRDC [m] (the cur-
rent page, one page=256 words) and TABRDL [m]
(the last page) transfer the contents of the lower-order
byte to the specified data memory, and the
Table Location
@5
@5
@5
*5
S5
#5
*5
0
PC+2
@4
@4
@4
*4
#4
S4
*4
0
HT48RA0-2/HT48CA0-2
Program Memory
@3
@3
@3
*3
S3
#3
*3
0
@2
@2
@2
*2
S2
#2
*2
0
@1
@1
@1
*1
#1
S1
*1
0
July 23, 2004
@0
@0
@0
S0
#0
*0
*0
0