HT46RU25 Holtek Semiconductor Inc., HT46RU25 Datasheet - Page 7

• Manufacturer Part Number: HT46RU25
• Description: Ht46ru25/ht46cu25 -- A/d Type 8-bit Mcu
• Manufacturer: Holtek Semiconductor Inc.

Functional Description
Execution Flow
The system clock is derived from either a crystal or an
RC oscillator or an 32768Hz crystal. It is internally di-
vided 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 decoding and ex-
ecution takes the next instruction cycle. The pipelining
scheme makes it possible for each instruction to be ef-
fectively executed in a cycle. If an instruction changes
the value of the program counter, two cycles are re-
quired to complete the instruction.
Note:
Rev. 1.30
Initial Reset
External Interrupt
Timer/Event Counter 0 Overflow
Timer/Event Counter 1 Overflow
UART Bus Interrupt
I
Multi-function Interrupt
Skip
Loading PCL
Jump, Call Branch
Return from Subroutine
2
C Bus Interrupt
*13~*0: Program counter bits
#12~#0: Instruction code bits
Mode
BP.5 #12 #11 #10
S13 S12 S11 S10 S9
*13 *12
*13 *12 *11 *10
0
0
0
0
0
0
0
0
0
0
0
0
0
0
*11
0
0
0
0
0
0
0
Program Counter
Execution Flow
Program Counter + 2 (Within the current bank)
*10
0
0
0
0
0
0
0
7
#9
*9
*9
0
0
0
0
0
0
0
Program Counter - PC
The program counter (PC) is 14 bits wide and it controls
the sequence in which the instructions stored in the pro-
gram ROM are executed. The contents of the PC can
specify a maximum of 16384 16 addresses. After ac-
cessing a program memory word to fetch an instruction
code, the value of the PC is incremented by 1. The PC
then points to the memory word containing the next in-
struction code. When executing a jump instruction, con-
ditional skip execution, loading a PCL register, a
subroutine call, an initial reset, an internal interrupt, an
external interrupt, or returning from a subroutine, the PC
S13~S0: Stack register bits
@7~@0: PCL bits
S8
#8
*8
*8
Program Counter
0
0
0
0
0
0
0
@7 @6 @5 @4 @3 @2 @1 @0
S7
#7
*7
0
0
0
0
0
0
0
S6
#6
*6
0
0
0
0
0
0
0
HT46RU25/HT46CU25
S5
#5
*5
0
0
0
0
0
0
0
#4
S4
*4
0
0
0
0
1
1
1
S3
#3
*3
0
0
1
1
0
0
1
S2
#2
*2
0
1
0
1
0
1
0
March 9, 2007
S1
#1
*1
0
0
0
0
0
0
0
S0
#0
*0
0
0
0
0
0
0
0