參數(shù)資料
型號: HT48CA1
廠商: Holtek Semiconductor Inc.
英文描述: Remote Type 8-Bit MCU
中文描述: 遠(yuǎn)程型8位微控制器
文件頁數(shù): 10/39頁
文件大?。?/td> 308K
代理商: HT48CA1
HT48RA1/HT48CA1
Rev. 1.00
10
June 25, 2004
cur. The related interrupt request flag (T1F) will be reset
and the EMI bit cleared to disable further interrupts.
During the execution of an interrupt subroutine, other in-
terrupt acknowledge signals are held until the RETI in-
struction is executed or the EMI bit and the related
interrupt control bit are set to 1 (if the stack is not full). To
return from the interrupt subroutine, RET or RETI
may be invoked. RETI will set the EMI bit to enable an in-
terrupt service, but RET will not.
Interrupts, occurring in the interval between the rising
edges of two consecutive T2 pulses, will be serviced on
the latter of the two T2 pulses, if the corresponding inter-
rupts are enabled. In the case of simultaneous requests
the following table shows the priority that is applied.
These can be masked by resetting the EMI bit.
Interrupt Source
Priority
Vector
External Interrupt
1
04H
Timer/Event Counter 0 Overflow
2
08H
Timer/Event Counter 1 Overflow
3
0CH
The Timer/Event Counter 0/1 interrupt request flag
(T0F/T1F), external interrupt request flag (EIF), enable
Timer/Event Counter 0/1 interrupt bit (ET0I/ET1I), en-
able external interrupt bit (EEI) and enable master inter-
rupt bit (EMI) constitute an interrupt control register
(INTC) which is located at 0BH in the data memory. EMI,
EEI, ET0I and ET1I are used to control the enabling/dis-
abling of interrupts. These bits prevent the requested in-
terrupt from being serviced. Once the interrupt request
flags(T0F,T1F,EIF)areset,theywillremainintheINTC
register until the interrupts are serviced or cleared by a
software instruction.
It is recommended that a program does not use the
CALL subroutine within the interrupt subroutine. In-
terrupts often occur in an unpredictable manner or
need to be serviced immediately in some applications.
If only one stack is left and enabling the interrupt is not
well controlled, the original control sequence will be dam-
aged once the CALL operates in the interrupt subrou-
tine.
Oscillator Configuration
There are 2 oscillator circuits implemented in the
microcontroller.
Both of them are designed for system clocks, namely
the RC oscillator and the crystal oscillator, which are de-
termined by options. No matter what oscillator type is
selected, the signal provides the system clock. The
HALT mode stops the system oscillator and resists the
external signal to conserve power.
If an RC oscillator is used, an external resistor between
OSC1 and VSS is required and the resistance should
range from 100k
by 4, is available on OSC2, which can be used to syn-
chronize external logic. The internal RC oscillator pro-
vides the most cost effective solution. However, the
frequency of oscillation may vary with VDD, tempera-
tures and the chip itself due to process variations. It is,
therefore, not suitable for timing sensitive operations
where an accurate oscillator frequency is desired.
to 820k . The system clock, divided
If the crystal oscillator is used, a crystal across OSC1
and OSC2 is needed to provide the feedback and phase
shift required for the oscillator, and no other external
components are demanded. Instead of a crystal, the
resonator can also be connected between OSC1 and
OSC2 to get a frequency reference, but two external ca-
pacitors in OSC1 and OSC2 are required.
The WDT oscillator is a free running on-chip RC oscilla-
tor, and no external components are required. Even if
the system enters the power down mode, the system
clock is stopped, but the WDToscillator still works with a
period of approximately 90 s. The WDT oscillator can
be disabled by ROM code option to conserve power.
Register
Bit No.
Label
Function
INTC
(0BH)
0
EMI
Controls the master (global) interrupt (1=enabled; 0=disabled)
1
EEI
Controls the external interrupt (1=enabled; 0=disabled)
2
ET0I
Controls the Timer/Event Counter 0 interrupt (1=enabled; 0=disabled)
3
ET1I
Controls the Timer/Event Counter 1 interrupt (1=enabled; 0=disabled)
4
EIF
External interrupt request flag (1=active; 0=inactive)
5
T0F
Internal Timer/Event Counter 0 request flag (1=active; 0=inactive)
6
T1F
Internal Timer/Event Counter 1 request flag (1=active; 0=inactive)
7
Unused bit, read as 0
INTC Register
.
* ! " 4
, " " ! * %
4
, " " ! * %
4
+
) 4
! , )
#
$
System Oscillator
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