AR# 34395: Spartan-6 Packaging - Why does the Spartan-6 LX45 have more pins than the LX75 in the FG(G)484 package?
Spartan-6 Packaging - Why does the Spartan-6 LX45 have more pins than the LX75 in the FG(G)484 package?
In the Spartan-6 Family Overview Data Sheet (DS160), Table 2 shows the device package combinations: http://www.xilinx.com/support/documentation/data_sheets/ds160.pdf The Spartan-6 LX75 device (XC6SLX75) shows less available I/Os in the FG(G)484 package than the Spartan-6 LX45 device (XC6SLX45) in that same package. Why is this?
The Device-Package Combination table is correct. The cause of the fewer available I/Os is that the LX75T adds another pair of GTP_DUAL at the bottom of the device. The LX45T has two GTP_DUAL, and the LX75T has four.Those additional two GTP_DUALs take away available I/O.The Spartan-6 devices use derived die technology; see (Xilinx Answer 34394), so the added GTP_DUALs have an impact on the LX devices, even though they do not use the GTPs.