AT89C51RC2-3CSCM 查看數據表（PDF） - Atmel Corporation

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AT89C51RC2-3CSCM

8-bit Microcontroller with 16K/32K Bytes Flash

Atmel Corporation 

Figure 50. Internal Clock Signals

INTERNAL

CLOCK

STATE4 STATE5

P1 P2 P1 P2

XTAL2

STATE6

P1 P2

STATE1

P1 P2

STATE2

P1 P2

STATE3

P1 P2

STATE4

P1 P2

STATE5

P1 P2

ALE

EXTERNAL PROGRAM MEMORY FETCH

PSEN

THESE SIGNALS ARE NOT ACTIVATED DURING THE

EXECUTION OF A MOVX INSTRUCTION

P0

P2 (EXT)

DATA

SAMPLED

FLOAT

PCL OUT

DATA

SAMPLED

FLOAT

PCL OUT

INDICATES ADDRESS TRANSITIONS

DATA

SAMPLED

FLOAT

PCL OUT

READ CYCLE

RD

P0

P2

DPL OR Rt OUT

DATA

SAMPLED

FLOAT

INDICATES DPH OR P2 SFR TO PCH TRANSITION

PCL OUT (IF PROGRAM

MEMORY IS EXTERNAL)

WRITE CYCLE

WR

P0

P2

DPL OR Rt OUT

PCL OUT (EVEN IF PROGRAM

MEMORY IS INTERNAL)

DATA OUT

INDICATES DPH OR P2 SFR TO PCH TRANSITION

PCL OUT (IF PROGRAM

MEMORY IS EXTERNAL)

PORT OPERATION

MOV PORT SRC

OLD DATA NEW DATA

MOV DEST P0

P0 PINS SAMPLED

MOV DEST PORT (P1. P2. P3) P1, P2, P3 PINS SAMPLED

(INCLUDES INTO. INT1. TO T1)

SERIAL PORT SHIFT CLOCK

TXD (MODE 0)

RXD SAMPLED

P0 PINS SAMPLED

P1, P2, P3 PINS SAMPLED

RXD SAMPLED

This diagram indicates when signals are clocked internally. The time it takes the signals to propagate to the pins, however,

ranges from 25 to 125 ns. This propagation delay is dependent on variables such as temperature and pin loading. Propaga-

tion also varies from output to output and component. Typically though (TA = 25°C fully loaded) RD and WR propagation

delays are approximately 50 ns. The other signals are typically 85 ns. Propagation delays are incorporated in the AC

specifications.

118 AT89C51RB2/RC2

4180E–8051–10/06

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