Maxim Integrated DS33Z41 - Manual (Page 29)

DS33Z41 Quad IMUX Ethernet Mapper
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8.7 Device Interrupts
Figure 8-2 diagrams the flow of interrupt conditions from their source status bits through the multiple levels of
information registers and mask bits to the interrupt pin. When an interrupt occurs, the host can read the Global
Latched Status registers
GL.LIS , GL.SIS , GL.IBIS , GL.TRQIS , GL.IMXSLS, GL.IMXDFDELS, and GL.IMXOOFLS
to initially determine the source of the interrupt. The host can then read the LI.TQCTLS , LI.TPPSRL , LI.RPPSRL ,
LI.RX86S , SU.QCRLS , and BSRL registers to further identify the source of the interrupt(s). In order to maintain
software compatibility with the multiport devices in the product family, the global interrupt status and interrupt
enable registers have been preserved, but do not need to be used. If
GL.TRQIS is determined to be the interrupt
source, the host will then read the LI.TPPSRL and LI.RPPSRL registers for the cause of the interrupt. If GL.LIS is
determined to be the interrupt source, the host will then read the LI.TQCTLS , LI.TPPSRL , LI.RPPSRL , and
LI.RX86S registers for the source of the interrupt. If GL.SIS is the source, the host will then read the SU.QCRLS
register for the source of the interrupt. If GL.IBIS is the source, the host will then read the BSRL register for the
source of the interrupt. All Global Interrupt Status Register bits are real-time bits that will clear once the
appropriate interrupt has been serviced and cleared, as long as no additional, enabled interrupt conditions are
present in the associated status register. All Latched Status bits must be cleared by the host writing a “1” to the bit
location of the interrupt condition that has been serviced. In order for individual status conditions to transmit their
status to the next level of interrupt logic, they must be enabled by placing a “1” in the associated bit location of the
correct Interrupt Enable Register. The Interrupt enable registers are
LI.TPPSRIE , LI.RPPSRIE , LI.RX86LSIE ,
BSRIE, SU.QRIE, GL.LIE, GL.SIE, GL.IBIE, GL.TRQIE, GL.IMXSIE, GL.IMXDFEIE, and GL.IMXOOFIE. Latched
Status bits that have been enabled via Interrupt Enable registers are allowed to pass their interrupt conditions to
the Global Interrupt Status Registers. The Interrupt enable registers allow individual Latched Status conditions to
generate an interrupt, but when set to zero, they do not prevent the Latched Status bits from being set. Therefore,
when servicing interrupts, the user should AND the Latched Status with the associated Interrupt Enable Register
in order to exclude bits for which the user wished to prevent interrupt service. This architecture allows the
application host to periodically poll the latched status bits for non-interrupt conditions, while using only one set of
registers. Note the bit-orders of SU.QRIE and SU.QCRLS are different.
Note that the inactive state of the interrupt output pin is configurable. The INTM bit in GL.CR1 controls the inactive
state of the interrupt pin, allowing selection of a pull-up resistor or active driver .
The interrupt structure is designed to efficiently guide the user to the source of an enabled interrupt source. The
latched status bits for the interrupting entity must be read to clear the interrupt. Also reading the latched status bit
will reset all bits in that register. During a reset condition, interrupts cannot be generated. The interrupts from any
source can be blocked at a global level by the placing a zero in the global interrupt enable registers (
GL.LIE ,
GL.SIE, GL.IBIE, GL.TRQIE, GL.IMXSIE, GL.IMXDFEIE, and GL.IMXOOFIE). Reading the Latched Status bit for
all interrupt generating events will clear the interrupt status bit and Interrupt signal will be deasserted.