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46
DMx820 User’s Manual
6.3.4
FIFO
C
HANNEL N
The DMx820HR provides two FIFOs to buffer data going into and out of the board. Each FIFO is 4MB in size. The input strobe, output strobe,
and data input for each FIFO can be individually selected. The output data is made available to the peripheral outputs, and also the PCI
interface.
Each FIFO is attached to a DMA Channel in the PLX chip. FIFO0 is attached to DMA0, and FIFO1 is attached to DMA1.
FIFOn_ID
ID register to identify a FIFO Block.
15
0
ID_Register
R
Field
Description
ID_Register15:0]
Value of 0x2011 indicates SDRAM/FIFO Block
FIFOn_INT
Enable and status for the interrupts generated by the FIFOs. An Overflow condition occurs when the FIFO is full, and it is written to. It can also
occur when the FIFO is written to too fast. An Underflow occurs when the FIFO is empty and the output clock toggles, or when the FIFO is
read from too fast. When the FIFO is disabled, the “Full,” “Empty,” and both requests are asserted.
15
8
7
0
INT_STAT[7:0]
INT_ENA[7:0]
RC,+0
RW,+0
Field
Description
INT_STAT[7:0]
Interrupt Status
– ‘1’ = Interrupt condition has occurred.
Write ‘1’ to clear. Interrupts are asserted on the
positive edge of the clock.
INT_ENA[7:0]
Interrupt Enable
– ‘1’ = Interrupt is enabled, ‘0’ = disabled
Interrupt source are:
7 Reserved
6 Reserved
5 Underflow
4 Overflow
3 Empty
2 Full
1 Write Request
0 Read Request
FIFOn_IN_CLK
This register selects the input clock to the FIFO. At every positive edge of the input clock, a word is read into the FIFO from the input source.
15
5
4
0
Reserved
CLOCK_SEL[4:0]
R,+0
RW,+0
Field
Description
CLOCK_SEL[4:0]
Selects the input clock input to this FIFO channel. Value
definitions are:
31 PCI Write to FIFOn_RW_PORT
30 PCI Read from FIFOn_RW_PORT
29 Prog. Clock 3 Interrupt
28 Prog. Clock 2 Interrupt
27 Prog. Clock 1 Interrupt
26 Prog. Clock 0 Interrupt