EM78P156E Ver la hoja de datos (PDF) - ELAN Microelectronics
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EM78P156E Datasheet PDF : 28 Pages
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EM78P156E
008H. Once in the interrupt service routine, the source of an interrupt can be determined by polling the flag bits
in RF. The interrupt flag bit must be cleared by instructions before leaving the interrupt service routine and
enabling interrupts to avoid recursive interrupts.
The flag (except ICIF bit) in the Interrupt Status Register (RF) is set regardless of the status of its mask bit or the
execution of ENI. Note that the outcome of RF will be the logic AND of RF and IOCF. Refer to Fig.10. The
RETI instruction ends the interrupt routine and enables the global interrupt (the execution of ENI).
When an interrupt is generated by the INT instruction (when enabled), the next instruction will be fetched from
address 001H
VCC
/IRQn
D
P
R
Q
CLK
CQ
L
RF
RPRD
IRQn
.
.
IRQm
/INT
ENI/DISI
Q
P
R
D
IOD
/RESET
CLK
QC
L
IOCF
IOCFWR
IOCFRD
VI.7 Oscillator
RFWR
Fig. 10 Interrupt input circuit
1. Oscillator Modes
EM78P156E can be operated in four different oscillator modes. There are Internal Capacitor oscillator mode (IRC),
External RC oscillator mode (ERC), High XTAL oscillator mode (HXT) and Low XTAL oscillator mode (LXT). Users
can select one of them by programming MS and HLF in the CODE option register. Table 6 depicts how these four modes
to be defined.
The up-limited operation frequency of crystal/resonator on the different VDDs is listed in Table 7.
Table 6 Oscillator Modes defined by MS, HLF, HLP and IRCEN
Mode
MS
External RC oscillator mode
0
High XTAL oscillator mode
1
Low XTAL oscillator mode
1
Internal C, External R oscillator mode
0
HLF
*X
1
0
*X
HLP
*X
*X
0
*X
IRCEN
1
*X
*X
0
<Note> 1. X, Do not care
2. The transient point of system frequency between HXT and LXY is around 400 KHz.
* This specification is subject to be changed without notice. 8.11.1999
B3-17
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