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EM78P221/2N
8-Bit Microcontroller with OTP ROM
Product Specification (V1.0) 10.19.2007 • 47
(This specification is subject to change without further notice)
LVR characteristics are set at Code Option Word 0, Bits 10 and 9. Detailed operation
mode is as follows:
Word 0
Bit 12 Bit 11 Bit 10 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
TYPE1 TYPE0 LVR1 LVR0 CLKS ENWDTB OSC2 OSC1 OSC0 - PR2 PR1 PR0
Bits 10~9 (LVR1 ~ LVR0): Low Voltage Reset enable bits. If Vdd has crossover at Vdd
reset level as Vdd changes, the system will reset.
LVR1, LVR0 VDD Reset Level VDD Release Level
11 NA (Power-on Reset) (default)
10 2.5V 2.7V
01 3.0V 3.2V
00 4.0V 4.2V
Vdd
Internal Reset
V
RESET
Vdd < Vreset not longer than 10us, the system still keeps on oper at i ng
<LVR Voltage drop
18ms
System occur reset
>LVR Voltage drop
Fig. 6-18 LVR Waveform Situation
6.11 Code Option
EM78P221/2N has two Code Option Words and one Customer ID word that are not a
part of the normal program memory.
Word 0 Word 1 Word 2
Bit 12 ~ Bit 0 Bit 12 ~ Bit 0 Bit 12 ~ Bit 0
6.11.1 Code Option Register (Word 0)
Word 0
Bit 12 Bit 11 Bit 10 Bit 9 Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
TYPE1 TYPE0 LVR1 LVR0 CLKS ENWDTB OSC2 OSC1 OSC0 - PR2 PR1 PR0