User guide

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

UG380 (v2.7) October 29, 2014

Chapter 5: Configuration Details

Configuration Packets

All Spartan-6 FPGA bitstream commands are executed by reading or writing to the

configuration registers. Configuration data is organized as 16-bit words. Some data can

occupy multiple words. There are three major commands that the configuration data can

contain: NOP, READ, and WRITE, shown in Table 5-23.

A configuration command is executed when the configuration command is read or written

to the appropriate command register.

Packet Types

All data (register writes and frame data) is encapsulated into two kinds of packets:

• Type 1 packet: contains two sections: Header and Data.

• Type 2 packet: contains three sections: Header, Word Count, and Data.

Type 1 Packet

A Type 1 packet is used for a register write with six address bits for a short block. The

Header section is always a 16-bit word. See Table 5-24.

The Type 1 data section follows the Type 1 packet header and contains the number of 16-bit

words specified by the word count portion of the header. See Table 5-25.

Type 2 Packet

The Type 2 packet, which must follow a Type 1 packet, is used to write long blocks. The

header section is always a 16-bit word.

Following the Type 2 packet header is the Type 2 data section, which contains the number

of 16-bit words specified by the word count portion of the header.

Table 5-23: Opcode Format

OP CODE

NOP 00

WRITE 10

Table 5-24: Type 1 Header Packet

Header Type Operation

Address

Word Count

Bits [15:13] [12:11] [10:5] [4:0]

Type 1 001 xx xxxxxx xxxxx

Table 5-25: Type 1 Data Section

Data [15:0]

Word xxxxxxxxxxxxxxxx