Xilinx Virtex-4 Configuration User Guide

Virtex-4 FPGA Configuration User Guide www.xilinx.com 101
UG071 (v1.12) June 2, 2017
Readback Command Sequences
R
Configuration Register Read Procedure (SelectMAP)
The simplest read operation targets a configuration register such as the COR or STAT
register. Any configuration register with read access can be read through the SelectMAP or
SelectMAP32 interface, although not all registers offer read access. The procedure for
reading the STAT register through the SelectMAP interface follows:
1. Write the Synchronization word to the device.
2. Write the read STAT register packet header to the device.
3. Write two dummy words to the device to flush the packet buffer.
4. Read four bytes if using SelectMAP or one 32-bit word if using SelectMAP32; this is the
Status register value.
5. Write the DESYNC command to the device
6. Write two dummy words to the device to flush the packet buffer.
The user must change the SelectMAP interface from write to read control between steps 3
and 4, and back to write control after step 4, as illustrated in Figure 8-2.
Table 8-1: Status Register Readback Command Sequence (SelectMAP)
Step
SelectMAP Port
Direction
Configuration
Data
Explanation
1WriteAA995566 Sync Word
2Write2800E001 Read 1 word from STAT register
3Write
20000000 NOOP
20000000 NOOP
4ReadSSSSSSSS
Device writes 1 word from the STAT
register to the configuration interface
5Write
30008001 Type 1 write 1 word to CMD
0000000D Desync command
6Write
20000000 NOOP
20000000 NOOP
Notes:
1. In 32-bit readback mode (e.g., ICAP), an extra NOOP should be inserted after the sync word.
Figure 8-2: SelectMAP Status Register Read
CS_B
RDWR_B
DATA[0:7]
WRITE
CCLK
AA 99 55 00
READ
UG071_49_010807
BUSY
SS
SS
SS
SS

Xilinx Virtex-4 Specifications

General

Brand	Xilinx
Model	Virtex-4
Category	Motherboard
Language	English