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MCF5272 User’s Manual
PLIC Timing Generator
interrupt. Once read, the interrupt is cleared. Each port and individual interrupts within each
port is maskable. The following conditions for each of the ports can trigger this interrupt:
•
Monitor channel receive: ASR defines which port or ports have generated a monitor
channel receive interrupt. The interrupt service routine must then read the
appropriate GMR register or registers to clear the monitor channel receive interrupt.
•
Monitor channel transmit: ASR defines which port or ports have generated a monitor
channel transmit interrupt. The interrupt service routine must then read the
appropriate GMT register or registers to clear the monitor channel transmit interrupt.
•
C/I channel receive: ASR defines which port or ports have generated a C/I channel
receive interrupt. The interrupt service routine must then read the appropriate GCIR
register or registers to clear the C/I channel receive interrupt.
•
C/I channel transmit: ASR defines which port or ports have generated a C/I channel
transmit interrupt. The interrupt service routine must then read the appropriate GCIT
register or registers to clear the C/I channel transmit interrupt.
13.2.5.3 Interrupt Control
There are a number of control mechanisms for the periodic and aperiodic interrupts on the
PLIC.
•
Clearing the ON/OFF bit in the port configuration register, Section 13.5.7, “Port
Configuration Registers (P0CR–P3CR),” turns the port off and masks all periodic
and aperiodic interrupts for the affected port.
•
Clearing the enable bits, ENB1 or ENB2, in the port configuration register masks the
periodic transmit and receive interrupts associated with the respective B1 or B2
channel.
•
Specific interrupt enables are provided in each port’s ICR. This includes a port
interrupt enable, IE, which masks all periodic and aperiodic interrupts. In addition,
there are interrupt enables for specific conditions. These are listed in Section 13.5.9,
“Interrupt Configuration Registers (P0ICR–P3ICR).”
13.3 PLIC Timing Generator
13.3.1 Clock Synthesis
The PLIC clock generator employs a completely digital, synchronous design which can be
used to synthesize a new clock by multiplying an incoming reference clock. This clock
generator is not a PLL—it has no VCO or phase comparator.
The frequency multiplication factor is always an integral power of two between 2 and 256
inclusive. The amount of phase jitter exhibited by the synthesized clock increases as the
synthesized clock frequency approaches CLKIN’s frequency. As a general guide, the
maximum generated DCL should be no greater than one-twentieth of CLKIN’s frequency.
Содержание DigitalDNA ColdFire MCF5272
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