NJU3504FA1 查看數據表（PDF） - Japan Radio Corporation

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NJU3504FA1

4-BIT SINGLE CHIP MICRO CONTROLLER

Japan Radio Corporation  

NJU3504

Though the data of the Timer and Counter can be read in the count operation, the read data is

sometimes incorrect when the clock inputs to the counter during the reading operation.

When the 8-bit counter data is read in count operation as shown in the following timing chart(An

example of data reading from the counter to RAM), Timer often counts up between the first 4-bit data

reading and the second. In case of the following chart, though the timer data is "0Fh" when the

lower 4-bit data is gotten, it is "10h" when the higher 4-bit data is gotten. Therefore the final data

becomes to be "1Fh".

[An example of data reading from the counter to RAM]

Counter clock

(prescaler

8 divide)

Timer Data

(8bit)

0D

0E

0F

10

11

12

Reading

Y-register

LSB

RAM

(4bit Y-address=0)

RAM

(4bit Y-address=1)

E

0

F

1

1

1

0Eh

1Fh:Incorrect data

11h

There are some other cases to read the incorrect data from the 8-bit counter during the count

operation depending on the relation with the external clock speed and the system execution speed.

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