User guide

66 www.xilinx.com Spartan-6 FPGA Configuration User Guide
UG380 (v2.7) October 29, 2014
Chapter 4: User Primitives
ICAP_SPARTAN6
The ICAP_SPARTAN6 primitive works similarly to the SelectMAP configuration interface
except it is on the fabric side, and ICAP has a separate read/write bus, as opposed to the
bidirectional bus in SelectMAP. ICAP also only supports x16 data width. The general
SelectMAP timing diagrams and the SelectMAP bitstream ordering information, as
described in SelectMAP Configuration Interface, page 30, are also applicable to ICAP. It
allows the user to access configuration registers and readback configuration data after
configuration is done.
ICAP data width is 16 bits for both input and output.
TCK Output The value of the TCK input pin to the FPGA.
TMS Output The value of the TMS input pin to the FPGA.
TDO Input TDO input driven from the user fabric logic. This signal is
internally sampled on the falling edge before being driven out
to the FPGA TDO pin.
Table 4-1: BSCAN_SPARTAN6 Port Descriptions (Cont’d)
Signal Name Type Function
Table 4-2: ICAP_SPARTAN6 Port Descriptions
Signal Type Function
CLK Input ICAP interface clock.
CE Input Active-Low ICAP interface select. Equivalent to CSI_B in the
SelectMAP interface.
WRITE Input Read/Write control input. 0 = WRITE, 1 = READ. Equivalent to
the RDWR_B signal in the SelectMAP interface.
I[15:0] Input 16-bit-wide ICAP write data bus. The bit ordering is identical to
the SelectMAP interface. See SelectMAP Data Ordering, page 39.
O[15:0] Output 16-bit-wide ICAP read data bus. The bit ordering is identical to the
SelectMAP interface. See SelectMAP Data Ordering in SelectMAP
Data Ordering, page 39. The ICAP output should be captured in a
device register.
The packet buffer must be cleared for read data from a command
to be presented on the O[15:0] bus. See Configuration Register
Read Procedure (SelectMAP) and Configuration Memory Read
Procedure (SelectMAP) for the correct procedure.
BUSY Output Active-High busy status. Only used in read operations. BUSY
remains Low during writes.