EM78156EAS EMC [ELAN Microelectronics Corp], EM78156EAS Datasheet - Page 26

• Manufacturer Part Number: EM78156EAS
• Description: 8-Bit Microcontroller with MASK ROM
• Manufacturer: EMC [ELAN Microelectronics Corp]

EM78156E
8-Bit Microcontroller with MASK ROM
22 •
4.7 Oscillator
4.7.1 Oscillator Modes
The EM78156E can be operated in three different oscillator modes, such as External
RC oscillator mode (ERC), High XTAL oscillator mode(HXT), and Low XTAL oscillator
mode(LXT). User can select one of them by programming MS and HLF in the CODE
option register. Table 8 depicts how these three modes are defined.
The up-most limited operation frequency of crystal/resonator on the different VDDs is
listed in Table 9.
Table 8 Oscillator Modes Defined by MS and HLP
Table 9 The Summary of Maximum Operating Speeds
4.7.2 .Crystal Oscillator/Ceramic Resonators(XTAL)
EM78156E can be driven by an external clock signal through the OSCI pin as shown in
Fig. 11 below.
ERC(External RC oscillator mode)
HXT(High XTAL oscillator mode)
LXT(Low XTAL oscillator mode)
1. X, Don’t care
2. The transient point of system frequency between HXT and LXY is around 400 KHz.
Two cycles with two clocks
EM78156E
Fig. 11 Circuit for External Clock Input
Conditions
OSCO
OSCI
Mode
(This specification is subject to change without further notice)
NOTE
Product Specification (V1.3) 07.29.2004
Ext. Clock
VDD
2.3
3.0
5.0
MS
0
1
1
Fxt max.(MHz)
20.0
4.0
8.0
HLF
*
1
0
X