Holtek HT46R22, Руководство пользователя

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Interrupts
The A/D series of microcontrollers each contain a range of both external and internal interrupt func-
tions. The external interrupt is controlled by the action of the external pin INT which is present on
all devices. Internal functions such as the timer counter, A/D converter and I
2
C interface all utilize
the internal interrupt function for their operation.
For the HT46R47/HT46C47 devices, which do not contain an internal I
2
C interface and contain
only a single timer, one 8-bit interrupt control register, known as INTC, is sufficient to control all the
required operations. As the HT46R22/HT46C22, HT46R23/HT46C23 and HT46R24/HT46C24 de-
vices both contain an I
2
C interface, a single 8-bit interrupt control register is insufficient to control
all the interrupt control features. For this reason two interrupt control registers are provided, known
as INTC0 and INTC1.
Once an interrupt subroutine is serviced, all the other interrupts will be blocked, by clearing the
EMI bit. This scheme may prevent any further interrupt nesting. Other interrupt requests may oc-
cur during this interval but only the interrupt request flag is recorded. If another interrupt requires
servicing while the program is in the interrupt service routine, the EMI bit should be set after enter-
ing the routine, to allow interrupt nesting. If the stack is full, the interrupt request will not be acknowl-
edged, even if the related interrupt is enabled, until the SP is decremented. If immediate service is
desired, the stack must be prevented from becoming full.
60
A/D Type MCU
S t a r t
H A A S = 1
?
H T X = 1
?
S R W = 1
?
Y e s N o
Y e s N o
R X A K = 1
?
Y e s
N o
N o
R e a d f r o m H D R
R E T I
Y e s
D u m m y R e a d
f r o m H D R
R E T I
R E T I
W r i t e t o H D R
S E T H T X
W r i t e t o H D R
D u m m y R e a d
F r o m H D R
C L R H T X
C L R T X A K
R E T I R E T I
C L R H T X
C L R T X A K
I
2
C Bus ISR Flow Chart