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the link port. The FIFO detects that there is room in the buffer and asserts another DMA request, continuing
the process.
LP Event Control
This section describes how the link port uses interrupts and status signals.
Interrupt Signals
Each link port has two dedicated interrupt lines registered with the system event controller—a data request interrupt
and a status interrupt. Data request interrupts are asserted based on FIFO conditions for data transfer. Status inter-
rupts are asserted when a service request status or an overflow status is set. The following list explains each of these
interrupts.
• Data Request Interrupt. Asserted if the FIFO is not full in transmission mode and the FIFO is not empty in
reception mode. This functionality serves as a core triggered interrupt in non-DMA mode and as the DMA
interrupt request in DMA mode. Generation of this interrupt is based on the LP_STAT.FFST (status bit of
the link port buffer).
• Link Port Transmit Service Request Interrupt (LTRQ). Allow a disabled link port to generate an interrupt
when an external access is attempted. When a link port is configured as transmitter, the transmit service request
interrupt is enabled by setting the LP_CTL.TRQMSK bit. When set, an external receiver can indicate to the
disabled transmitter that it must receive data through the connected link port. The receiver does so by driving a
high level on the LP_ACK line. When the LP_ACK of the disabled transmitter link port is detected high, a
LP_STAT.LTRQ interrupt is generated. The transmitter can enable itself for data transfer with the receiver.
The link port needs a pull-down on LP_ACK for this feature to function properly.
• Link Port Receive Service Request Interrupt (LRRQ). When a link port is configured as receiver, this interrupt
is enabled by setting the LP_CTL.RRQMSK bit. When set, an external transmitter can indicate to the disabled
receiver that it must receive data through the connected link port. The transmitter does so by driving out the
first data. When the LP_CLK of the disabled receiver link port is detected high, a LP_STAT.LRRQ interrupt
is generated. The receiver can further enable itself for data transfer with the transmitter. The link port needs a
pull-down on the LP_CLK signal for this feature to function properly.
• Link Port Receive Overflow Interrupt (LPOVF). Generated when the receiver FIFO overflows and is enabled
by setting the LP_CTL.ROVFMSK bit. This interrupt can happen if the transmitter continues to transmit data
even though the receiver has deasserted LP_ACK signal causing the receive FIFO to overflow.
Enabling Link Port Interrupts
A data request interrupt is fed to the system event controller directly and can be controlled separately from the appli-
cation.
To mask the interrupt, set the mask bits in
interrupt. These interrupts are OR'ed and fed to the SIC as a single
ed and stored in the associated bits of
ADSP-SC58x/ADSP-2158x SHARC+ Processor Hardware Reference
LP_CTL
register corresponding to service interrupts and the overflow
LP_STAT
register. If an
interrupt. These interrupts are latch-
LP_STAT
LP_STAT
interrupt occurs, in the ISR, programs
LP Event Control
15–13
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