Interrupts
4-20
ADSP-214xx SHARC Processor Hardware Reference
If the DMA is disabled but the associated link buffer is enabled, then a
maskable interrupt is generated whenever a receive buffer is not empty or
when a transmit buffer is not full. This interrupt is the same interrupt vec-
tor associated with the completion of the DMA block transfers.
The interrupt latch bit may be unmasked by the corresponding mask bit
in the same register. When initially enabling the mask bit, the correspond-
ing latch bit should be cleared first to clear out any request that may have
been inadvertently latched.
The interrupt service routine should test the buffer status or write to check
when the buffer is empty or full, in order to determine when it should
return from interrupt. This reduces the number of interrupts the ISR
must service.
For core interrupts programs need to perform two writes to the transmit
buffer to fill it. For the receiver, programs need to perform two reads from
the receive buffer to empty it. Then the next interrupt occurs when the
buffer becomes not full or not empty again. Two reads and or writes are
performed because the link port FIFO depth is two.
Service Request Interrupts
Link port service requests let a disabled (unassigned or assigned with buf-
fer disabled) link port cause an interrupt when an external access is
attempted. The transmit (
LTRQ
) and receive (
LRRQ
) request status bits of
the
LCTLx
register indicate when another processor is attempting to send
or receive data through a particular link port. Two processors can commu-
nicate without prior knowledge of the transfer direction, link port
number, or exactly when the transfer is to occur. The
LCTLx
register is
described in regs appendix.
When
LxACK
or
LxCLK
is asserted externally, a link service request (LSR) is
generated in a disabled (unassigned or assigned with buffer disabled) link
port. Each LSR is gated by mask bits before being latched in the
LSTATx
register. The two possible receive LSRs and the two possible transmit
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Содержание SHARC ADSP-214 Series
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Страница 1132: ...Register Listing A 306 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 1192: ...Index I 34 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...