EM78P342NP datasheet(62/102 Pages) EMC

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EM78P341N/342N/343N

8-Bit Microprocessor with OTP ROM

•

Product Specification (V1.0) 12.01.2006

(This specification is subject to change without further notice)

Bit 5 ~ Bit 3 (VOF[2] ~ VOF[0]): Offset voltage bits

VOF[2]

VOF[1]

VOF[0]

EM78P342N/343N

ICE342N

0LSB

2LSB

4LSB

6LSB

8LSB

10LSB

12LSB

14LSB

Bit 2 ~ Bit 0: Unimplemented, read as ‘0’.

6.7.2 ADC Data Register (ADDATA/RB, ADDATA1H/RC, ADDATA1L/RD)

When the AD conversion is completed, the result is loaded to the ADDATA, ADDATA1H

and ADDATA1L registers. The ADRUN bit is cleared, and the ADIF is set.

6.7.3 ADC Sampling Time

The accuracy, linearity, and speed of the successive approximation of AD converter are

dependent on the properties of the ADC and the comparator. The source impedance

and the internal sampling impedance directly affect the time required to charge the

sample holding capacitor. The application program controls the length of the sample

time to meet the specified accuracy. Generally speaking, the program should wait for

µs for each KΩ of the analog source impedance and at least 2µs for the low-impedance

source. The maximum recommended impedance for analog source is 10K

Ω at Vdd=5V.

After the analog input channel is selected, this acquisition time must be done before the

conversion is started.

6.7.4 AD Conversion Time

CKR1 and CKR0 select the conversion time (Tct), in terms of instruction cycles. This

allows the MCU to run at a maximum frequency without sacrificing the AD conversion

accuracy. For the EM78P342N/343N, the conversion time per bit is 4

µs. The table

below shows the relationship between Tct and the maximum operating frequencies.

CKR1: CKR0 Operation Mode

Max. Operation

Frequency

Max. Conversion

Rate/Bit

Max. Conversion Rate

Fsco/16

4 MHz

250kHz (4µs)

×4µs=60µs(16.7kHz)

Fsco/4

1MHz

250kHz (4µs)

×4µs=60µs(16.7kHz)

Fsco/64

16MHz

250kHz( 4µs)

×4µs=60µs(16.7kHz)

Fsco/8

2MHz

250kHz (4µs)

×4µs=1065µs(16.7kHz)

NOTE

■ Pin not used as an analog input pin can be used as a regular input or output pin.

■ During conversion, do not perform output instruction to maintain precision for all of

the pins.

EM78P342NP Datasheet(PDF) 62 Page - ELAN Microelectronics Corp

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