EM78P341N/342N/343N
8-Bit Microprocessor with OTP ROM
Bit 5 ~ Bit 3 (VOF[2] ~ VOF[0]): Offset voltage bits
VOF[2]
VOF[1]
VOF[0]
EM78P342N/343N
ICE342N
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0LSB
2LSB
4LSB
6LSB
8LSB
10LSB
12LSB
14LSB
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
2µs 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 10KΩ 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 4µs. The table
below shows the relationship between Tct and the maximum operating frequencies.
Max. Operation Max. Conversion
CKR1: CKR0Operation Mode
Max. Conversion Rate
Frequency
Rate/Bit
00
01
10
11
Fsco/16
Fsco/4
Fsco/64
Fsco/8
4 MHz
250kHz (4µs) 15×4µs=60µs(16.7kHz)
250kHz (4µs) 15×4µs=60µs(16.7kHz)
250kHz( 4µs) 15×4µs=60µs(16.7kHz)
250kHz (4µs) 15×4µs=1065µs(16.7kHz)
1MHz
16MHz
2MHz
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.
56 •
Product Specification (V1.0) 12.01.2006
(This specification is subject to change without further notice)
ELAN [ ELAN MICROELECTRONICS CORP ]
