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CY_INIT

Initialization Stage for Carry Chain

XC3000
XC4000E
XC4000X
XC5200
XC9000
Spartan
SpartanXL
Virtex
N/A
N/A
N/A
Macro
N/A
N/A
N/A
N/A

figures/x4924n.gif

CY_INIT is used to initialize the carry chain in the XC5200 architecture. It is used in conjunction with multiple CY_MUX elements to implement high speed carry-propagate or high speed cascade logic. CY_INIT must be placed in the logic cell (LC) immediately below the least-significant carry element (CY_MUX) in the carry/cascade chain. The INIT input is driven from the direct input (DI) to LC. The CY_INIT carry-out (COUT) drives the C in input of the first LC in the carry chain. The COUT output reflects the state of the DI input. This figure represents the schematic implementation of CY_INIT.

Figure 4.52 CY _INIT 4-Bit Adder Implementation XC5200

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