HT48CA0-1 Holtek Semiconductor, HT48CA0-1 Datasheet - Page 4

• Manufacturer Part Number: HT48CA0-1
• Description: (HT48RA0-1 / HT48CA0-1) Remote Type 8-Bit MCU
• Manufacturer: Holtek Semiconductor

www.DataSheet4U.com
A.C. Characteristics
Note: t
Functional Description
Execution Flow
The HT48RA0-1/HT48CA0-1 system clock can be de-
rived from a crystal/ceramic resonator oscillator. It is in-
ternally divided into four non-overlapping clocks. One
instruction cycle consists of four system clock cycles.
Instruction fetching and execution are pipelined in such
a way that a fetch takes one instruction cycle while de-
coding and execution takes the next instruction cycle.
However, the pipelining scheme causes each instruc-
tion to effectively execute within one cycle. If an instruc-
tion changes the program counter, two cycles are
required to complete the instruction.
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
Rev. 1.40
Symbol
f
t
t
t
SYS
RES
SST
LVR
SYS
=1/f
System Clock
External Reset Low Pulse Width
System Start-up Timer Period
Low Voltage Width to Reset
SYS
Parameter
V
3V
DD
Execution Flow
Power-up, reset or wake-up
from HALT
Test Conditions
4
Conditions
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
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:
Location 000H
This area is reserved for the initialization program. Af-
ter chip reset, the program always begins execution at
location 000H.
HT48RA0-1/HT48CA0-1
Min.
400
1
1
1024
Typ.
December 21, 2005
Max.
4000
Ta=25 C
Unit
t
kHz
ms
SYS
s