ht82k95ee Holtek Semiconductor Inc., ht82k95ee Datasheet - Page 6

• Manufacturer Part Number: ht82k95ee
• Description: Ht82k95ee/ht82k95ae -- Usb Multimedia Keyboard Encoder 8-bit Mcu
• Manufacturer: Holtek Semiconductor Inc.

Functional Description
Execution Flow
The system clock for the microcontroller is derived from
a crystal. The system clock is internally 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 an instruction cycle while de-
coding and execution takes the next instruction cycle.
However, the pipelining scheme allows each instruction
to be effectively executed in a cycle. If an instruction
changes the program counter, two cycles are required to
complete the instruction.
Program Counter - PC
The program counter (PC) controls the sequence in
which the instructions stored in the program ROM are
executed and its contents specify a full range of pro-
gram memory.
After accessing a program memory word to fetch an in-
struction code, the contents of the program counter are
Note: *11~*0: Program counter bits
Rev. 1.20
Initial reset
USB interrupt
Timer/Event Counter 0 overflow
Timer/Event Counter 1 overflow
Skip
Loading PCL
Jump, call branch
Return from subroutine
#11~#0: Instruction code bits
Mode
S11
#11
*11
*11
0
0
0
0
#10
S10
*10
*10
0
0
0
0
Program Counter
S9
Execution Flow
#9
*9
*9
0
0
0
0
S8
#8
*8
*8
0
0
0
0
6
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 or return
from subroutine, initial reset, internal interrupt, external
interrupt or return from interrupts, the PC manipulates
the program transfer by loading the address corre-
sponding to each instruction.
The conditional skip is activated by instructions. 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 to 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 the current program ROM page.
When a control transfer takes place, an additional
dummy cycle is required.
S11~S0: Stack register bits
@7~@0: PCL bits
@7
S7
#7
*7
0
0
0
0
Program Counter+2
Program Counter
@6
#6
S6
*6
0
0
0
0
@5
HT82K95EE/HT82K95AE
S5
#5
*5
0
0
0
0
@4
S4
#4
*4
0
0
0
0
@3
S3
#3
*3
0
0
1
1
@2
#2
S2
*2
0
1
0
1
August 28, 2006
@1
S1
#1
*1
0
0
0
0
@0
S0
#0
*0
0
0
0
0