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3.2 EMAC Control Module Interrupt Timer Count Register (EWINTTCNT)
EMAC Control Module Registers
The EMAC control module interrupt timer count register (EWINTTCNT) is used to control the generation
of back-to-back interrupts from the EMAC and MDIO modules. The value of this timer count is loaded
into an internal counter every time interrupts are enabled using the INTEN bit in the EMAC control
module interrupt control register (EWCTL). A second interrupt cannot be generated until this count
reaches 0. The counter is decremented at a frequency of PLL1clock/6; the default reset count is 0
(inactive) and the maximum value is 1 FFFFh (131 071).
The EWINTTCNT is shown in Figure 12 and described in Table 9 .
Figure 12. EMAC Control Module Interrupt Timer Count Register (EWINTTCNT)
31 17 16
Reserved EWINTTCNT
R-0 R/W-0
15 0
EWINTTCNT
R/W-0
LEGEND: R = Read only; R/W = Read/Write; - n = value after reset
Table 9. EMAC Control Module Interrupt Timer Count Register (EWINTTCNT) Field Descriptions
Bit Field Value Description
31-18 Reserved 0 Reserved
17-0 EWINTTCNT 0-1 FFFFh Interrupt timer count. EWINTTCNT is a 17-bit interrupt timer count that is used to control the
generation of back-to-back interrupts from the EMAC and MDIO modules. The value of
EWINTTCNT is loaded in an internal time counter every time interrupts are enabled by
writing a 1 to the INTEN bit in EWCTL (note the INTEN bit must transition from 0 to 1 to
initialize the internal time counter). Once initialized, the time counter will count down with
each peripheral clock until it reaches 0. A second interrupt cannot be generated until this
counter reaches 0. Any time the time counter has a non-zero value, the interrupt logic will
block the EMAC_MDIO_INT interrupt to the CPU. Thus, if any of the interrupts coming to the
EMAC control module is asserted, the interrupt logic will assert the EMAC_MDIO_INT signal
to the CPU, provided the INTEN bit in EWCTL is set, and the time counter value is 0.
54 Ethernet Media Access Controller (EMAC)/ SPRU941A – April 2007
Management Data Input/Output (MDIO)
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