HT83F40P datasheet(7/61 Pages) HOLTEK

7 / 61 page

HT83FXX

Rev. 1.00

May 12, 2009

System Architecture

A key factor in the high-performance features of the

Holtek range of Voice microcontrollers is attributed to

the internal system architecture. The range of devices

take advantage of the usual features found within RISC

microcontrollers providing increased speed of operation

and enhanced performance. The pipelining scheme is

implemented in such a way that instruction fetching and

instruction execution are overlapped, hence instructions

are effectively executed in one cycle, with the exception

of branch or call instructions. An 8-bit wide ALU is used

in practically all operations of the instruction set. It car-

ries out arithmetic operations, logic operations, rotation,

increment, decrement, branch decisions, etc. The inter-

nal data path is simplified by moving data through the

Accumulator and the ALU. Certain internal registers are

implemented in the Data Memory and can be directly or

indirectly addressed. The simple addressing methods of

these registers along with additional architectural fea-

tures ensure that a minimum of external components is

required to provide a functional I/O, voltage type DAC,

PWM direct drive output, capacitor/resistor sensor input

and external RC oscillator converter with maximum reli-

ability and flexibility.

Clocking and Pipelining

The main system clock, derived from either a Crystal/

Resonator or RC oscillator is subdivided into four inter-

nally generated non-overlapping clocks, T1~T4. The

Program Counter is incremented at the beginning of the

T1 clock during which time a new instruction is fetched.

The remaining T2~T4 clocks carry out the decoding and

execution functions. In this way, one T1~T4 clock cycle

forms one instruction cycle. Although the fetching and

execution of instructions takes place in consecutive in-

struction cycles, the pipelining structure of the

microcontroller ensures that instructions are effectively

executed in one instruction cycle. The exception to this

are instructions where the contents of the Program

Counter are changed, such as subroutine calls or

jumps, in which case the instruction will take one more

instruction cycle to execute.

When the RC oscillator is used, OSC2 can be used used

as a T1 phase clock synchronizing pin. This T1 phase

clock has a frequency of fSYS/4 with a 1:3 high/low duty

cycle.

For instructions involving branches, such as jump or call

instructions, two machine cycles are required to com-

plete instruction execution. An extra cycle is required as

the program takes one cycle to first obtain the actual

jump or call address and then another cycle to actually

execute the branch. The requirement for this extra cycle

should be taken into account by programmers in timing

sensitive applications.

F e t c h I n s t . ( P C )

E x e c u t e I n s t . ( P C - 1 )

F e t c h I n s t . ( P C + 1 )

E x e c u t e I n s t . ( P C )

F e t c h I n s t . ( P C + 2 )

E x e c u t e I n s t . ( P C + 1 )

P C

P C + 1

P C + 2

O s c i l l a t o r C l o c k

( S y s t e m C l o c k )

P h a s e C l o c k T 1

P r o g r a m C o u n t e r

P h a s e C l o c k T 2

P h a s e C l o c k T 3

P h a s e C l o c k T 4

P i p e l i n i n g

System Clocking and Pipelining

F e t c h I n s t . 1

E x e c u t e I n s t . 1

F e t c h I n s t . 2

F l u s h P i p e l i n e

D E L A Y :

M O V A , [ 1 2 H ]

C A L L D E L A Y

C P L [ 1 2 H ]

N O P

E x e c u t e I n s t . 2

F e t c h I n s t . 3

F e t c h I n s t . 6

E x e c u t e I n s t . 6

F e t c h I n s t . 7

Instruction Fetching

HT83F40P 数据表(PDF) 7 Page - Holtek Semiconductor Inc

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