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DS698 Datasheet, PDF (16/27 Pages) Xilinx, Inc – XPS InSystem Flash
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XPS InSystem Flash (v1.01b)
register contains a four-bit, right-justified value that is one less than the number of elements in the FIFO
(occupancy minus one).
This register is a read only. The effect of a write to it (or of a read when the FIFO is empty) will not affect
the register contents. The only reliable way to determine that the FIFO is empty is by reading the
Tx_Empty status bit in the SPI Status Register or the DTR Empty bit in the Interrupt Status Register.
The Transmit FIFO Occupancy register is shown in Figure 8, while the specifics of the data format is
described in Table 11.
Figure Top x-ref 8
Reserved
Occupancy
Value
0
27 28
31
DS698_08_072709
Figure 8: SPI Transmit FIFO Occupancy Register (C_BASEADDR + 0x74)
Table 11: SPI Transmit FIFO Occupancy Register Description (C_BASEADDR + 0x74)
Bit(s) Name
0 - 27
28 - 31
Reserved
Occupancy
Value
Core
Access
N/A
Read
Reset
Value
(hex)
N/A
0
Description
Reserved
Bit 28 is the MSB. The binary value plus 1 yields the
occupancy.
SPI Receive FIFO Occupancy Register (Rx_FIFO_OCY)
The SPI Receive FIFO Occupancy Register is present if and only if XPS InSystem Flash IP Core is
configured with FIFOs (C_FIFO_EXIST = 1). If it is present and if the Receive FIFO is not empty, the
register contains a four-bit, right-justified value that is one less than the number of elements in the FIFO
(occupancy minus one).
This register is a read only. The effect of a write to it (or of a read when the FIFO is empty) will not affect
the register contents. The write operation is not recommended on this register. The only reliable way to
determine that the FIFO is empty is by reading the Rx_Empty status bit in the SPI Status Register.
The Receive FIFO Occupancy register is shown in Figure 9, while the specifics of the data format is
described in Table 12.
Figure Top x-ref 9
Reserved
Occupancy
Value
0
27 28
31
DS698_09_072709
Figure 9: SPI Receive FIFO Occupancy Register (C_BASEADDR + 0x78)
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DS698 September 16, 2009
Product Specification
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