B3-20

EM78P156E

Table 9 RC Oscillator Frequencies

Cext

Rext

Average Fosc @ 5V, 25

°C

Average Fosc @ 3V, 25

°C

3.3k

3.92 MHz

3.65 MHz

5.1k

2.67 MHz

2.60 MHz

10k

1.39 MHz

1.40 MHz

100k

1.49 KHz

156 KHz

3.3k

1.39 MHz

1.33 MHz

5.1k

940 KHz

920 KHz

10k

480 KHz

475 KHz

100k

52 KHz

50 KHz

3.3k

595 KHz

560 KHz

5.1k

400 KHz

390 KHz

10k

200 KHz

200 KHz

100k

21 KHz

20 KHz

* 1. Measured on DIP packages.

2. Design reference only

4.

IRC Oscillator Mode

In IRC mode, it consists of an internal C which default frequency value is 4MHz. We suggest that the external Resistant

value here should be 50K

Ω connected to vdd with internal C.

VI.8 CODE Option Register

1.

Code Option Register

The EM78P156E has one Code option register which is not a part of the normal program memory. The option bits

can not be accessed during normal program execution.

12

11

10

9

8

7

6

5~0

MS

ENWDTB

CLKS

PTB

HLF

IRCEN

HLP

------

Bit 12 (MS): Oscillator type selection.

0: RC type

1: XTAL type (XTAL1 and XTAL2)

Bit 11 (ENWDTB): Watchdog Timer enable.

0: Enable

1: Disable

Bit 10 (CLKS): Instruction period option.

0: two oscillator periods

1: four oscillator periods

Refer to the section of Instruction Set.

Bit 9 (PTB): Protect bit

0: Enable

1: Disable

Bit 8 (HLF): XTAL frequency selection.

0: XTAL2 type (Low frequency, 32.768KHz)

300pF

100pF

20pF