EM78P257
OTP ROM
0: Enable
1: Disable
• Bit 10 (CLKS): Instruction period option bit.
0: Two clocks
1: Four clocks
Refer to the section on Instruction Set.
• Bit 9, 8 and 7 (OSC2,OSC1 and OSC0): Oscillator Modes Selection bits.
Table 32 Oscillator Modes Defined by OSC2,OSC1 and OSC0
Mode
OSC2
OSC1
OSC0
IRC(Internal RC oscillator mode)
IC(Internal C oscillator mode)
ERC(External RC oscillator mode)
HXT(High XTAL oscillator mode)
LXT(Low XTAL oscillator mode)
1
1
1
0
0
1
1
0
0
0
1
0
1
1
0
<Note> The transient point of system frequency between HXT and LXY is around 400 KHz.
• Bit 6 (/PTB): Protect bit.
0: Enable
1: Disable
• Bit 5 (SUT): Set-Up Time of device bits.
SUT
*Set-Up Time
1
0
18 ms
1 ms
*Theoretical values, for reference only
• Bit 4 (TYP): Type selection for EM78P257A or EM78P257B.
TYPE
Series
0
1
EM78P257B
EM78P257A
• Bit 3 (RCOUT): A selecting bit of Oscillator Output or I/O port for RC Oscillator.
RCOUT
Pin Function
0
1
P70
OSCO
• Bit 2, and Bit 1 ( RCM1, RCM0): IRC mode selection bits
RCM 1
RCM 0
*Frequency(MHz)
1
1
0
0
1
0
1
0
4
1
455kHz
32.768kHz
<Note> *Theoretical values, for reference only. In fact, the values may be inaccurate by ±35%.
• Bit0 : Not used
This specification is subject to change without prior notice.
66
07.27.2004 (V1.4)
ELAN [ ELAN MICROELECTRONICS CORP ]
