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PCI CD/CDa Configurable DMA Interface User’s Guide Registers

EDT, Inc. May 2007 33

Interface Configuration Register

Size 8-bit

I/O read-write

Address 0x0F

Access PCD_CONFIG

Figure 8 shows the structure of a 32-bit data word, with no swapping in effect. With SHORTSWAP set,

short 0 appears before short 1. With BYTESWAP set, byte 2 appears before byte 3, and byte 0 before

byte 1. With both set, byte 0 appears first, followed by byte 1, byte 2, and finally byte 3.

Figure 8. Data Word Structure Without Swapping

Bit PCD_ Description

7 SETIDV Set input data valid (used for debugging).

6 PIOEN Enables programmed I/O. A value of 1 translates DMA channel

buffers and enables the Programmed I/O Low Register and the

Programmed I/O High Register. Write the desired 16-bit word, the

low eight bits first to the Programmed I/O Low Register, and then the

high eight bits to the Programmed I/O High Register. When the

Programmed I/O High Register is written to, the firmware generates

an ODV pulse in mid-clock, to enable the device to latch the data.

5 SETDNR Set this bit to stop transfer to the device, as if the device had set DNR.

4 DED Disable output delay. If set, may cause ODV transitioning on DMA

start and underflows.

3 SHORTSWAP Set to 1 if the host computer writes the first 16-bit word on bits 16–31

of the PCI data bus (bigendian format) instead of bits 0–15 as defined

in the PCI Bus specification. See Figure 8 for the details of data word

structure.

2 SETAV64 PCI CDa only: For debugging. Set to tell PCI Xilinx that data is always

available.

PCI CD: not used

1 SELRXT PCI CDa only: Set to select RXT as the source for TXT and SENDT.

(See Table 1 on page 14 for descriptions of these signals.)

PCI CD: not used

0 BYTESWAP A value of 1 swaps the order of bytes in a 16-bit word of data coming

in from the data source. See Figure 8 for the details of data word

structure.

short 1 short 0

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

byte 3 byte 2 byte 1 byte 0

1 2 ... 32 33 34 35 36 37 38 39 40

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CDA CD 60 Betriebsanweisung Seite 37