User guide

Spartan-6 FPGA Configuration User Guide www.xilinx.com 39

UG380 (v2.7) October 29, 2014

SelectMAP Configuration Interface

Notes relevant to Figure 2-10:

1. The Data pins are in the High-Z state while CSI_B is deasserted. The data bus can be x8

or x16.

2. RDWR_B has no effect on the device while CSI_B is deasserted.

3. CSI_B is asserted by the user. The device begins loading configuration data on rising

CCLK edges.

4. A byte is loaded on the rising CCLK edge.

5. A byte is loaded on the rising CCLK edge.

6. A byte is loaded on the rising CCLK edge.

SelectMAP Data Ordering

In many cases, SelectMAP configuration is driven by a user application residing on a

microprocessor, CPLD, or in some cases another FPGA. In these applications, it is

important to understand how the data ordering in the configuration data file corresponds

to the data ordering expected by the FPGA.

In SelectMAP x8 mode, configuration data is loaded at one byte per CCLK, with the MSB

of each byte presented to the D0 pin. This convention (D0 = MSB, D7 = LSB) differs from

many other devices. For x16 modes, see Parallel Bus Bit Order, page 79. This convention

can be a source of confusion when designing custom configuration solutions. Table 2-4

shows how to load the hexadecimal value 0xABCD into the SelectMAP data bus.

Some applications can accommodate the non-conventional data ordering without

difficulty. For other applications, it can be more convenient for the source configuration

data file to be bit swapped, meaning that the bits in each byte of the data stream are reversed.

For these applications, the Xilinx PROM file generation software can generate bit-swapped

PROM files (see Configuration Data File Formats, page 75).

Table 2-5 shows the bit ordering for x8 and x16 modes.

Table 2-4: Bit Ordering for SelectMAP 8-Bit Mode

CCLK Cycle Hex Equivalent D0 D1 D2 D3 D4 D5 D6 D7

1 0xAB 1 0 1 0 1 0 1 1

2 0xCD 1 1 0 0 1 1 0 1

Notes:

1. D[0:7] represent the SelectMAP DATA pins.

Table 2-5: Spartan-6 FPGA Bit Ordering

Mode

Pins

1514131211109876543210

x16 8 9

01234567

x8 01234567