IN16C1054
6.4 Interrupts
As there are four independent 1-channel UARTs in SB16C1054, so there are four
interrupts. Interrupts are assigned INT0, INT1, INT2, and INT3 for each channel. Each
interrupt has six prioritized level’s interrupt generation capability. The IER enables each of
the six types of interrupts and INT signal in response to an interrupt generation. When an
interrupt is generated, the ISR indicates that an interrupt is pending and provides the type
of interrupt. And SB16C1054 can handle for four interrupts with one global interrupt.
Global interrupt treats four of each interrupt as one interrupt, so it is useful when external
system has few interrupt resource. Global interrupt line is also used as INT0, and it is
determined by AFR[4] that which one is used. If AFR[4] is cleared to ‘0’, INT0/GINT pin is
selected as INT0 and if set to ‘1’, GINT. When you treat four interrupts as one interrupt,
you should use several additional functions. GICR determines whether global interrupt
occurs or not. While GICR[0] is set to ‘1’, an interrupt that is generated in four one-
channel UARTs and treated as UNMASK is transmitted to GINT. But if GICR[0] is cleared
to ‘0’, an interrupt is not transmitted to GINT though interrupts are generated in four one-
channel UARTs and treated as MASK. So this interrupt is not transmitted to external
CPU. The status of global interrupt and generation of interrupts in one-channel UART can
be verified by GISR. The value set in GICR[0] is reflected in GISR[7], so the status of
mask of global interrupt can be verified. GISR[0] shows the status of interrupt of UART
that is connected to CS0#. If GISR[0] is cleared to ‘0’, it means that interrupt is not
generated in the UART of CS0# and if set to ‘1’, it means that interrupt is generated. The
value of GISR[0] shows the status of interrupt generated in the UART of CS0#,
irrespective of the value set in GICR[0]. GICR[0] determines whether the interrupts
generated in four one-channel UARTs that is connected to CS0#, CS1#, CS2#, and CS3#
are transmitted to external devices or not, but does not determine whether the interrupts
are generated or not in UARTs. The value of output signal when an interrupt is generated
in GINT pin is selected by AFR[5]. That is, GINT can determine the polarity of asserted
status. If AFR[5] is cleared to ‘0’, GINT outputs ‘0’ when global interrupt is generated. And
if set to ‘1’, outputs ‘1’ when global interrupt is generated.
Rev. 00
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