发明名称 |
High performance product term based carry chain scheme |
摘要 |
A macrocell for a programmable logic device includes a carry generator for generating a carry input to the macrocell, the carry generator having an inverting input and at least one non-inverting input. A carry decoupler controls the carry generator and allows any macrocell to be decoupled from a next adjacent macrocell. An XOR gate having a first input is coupled to the output of the carry generator and a second input thereof is connected to a logic input to the macrocell. A register is coupled to the output of the XOR gate. A macrocell output selector includes a first input coupled to an output of the register and a second input coupled to the output of the XOR gate. A method for implementing a carry chain for macrocells within a product term based programmable logic device according to the present invention includes the steps of logically ANDing a carry input with a user-configurable input to produce an intermediate result; selecting one of two carry input product terms from a product term array based upon the intermediate result, the selected carry product term being a carry input to a current macrocell; propagating the carry input of the current macrocell to a next macrocell; and repeating the ANDing, selecting and propagating steps until a last macrocell of the chain is reached.
|
申请公布号 |
US6201409(B1) |
申请公布日期 |
2001.03.13 |
申请号 |
US20000499816 |
申请日期 |
2000.02.08 |
申请人 |
CYPRESS SEMICONDUCTOR CORP. |
发明人 |
JONES CHRISTOPHER W.;MARSHALL JEFFERY MARK |
分类号 |
G06F7/50;G06F7/506;(IPC1-7):H03K19/177 |
主分类号 |
G06F7/50 |
代理机构 |
|
代理人 |
|
主权项 |
|
地址 |
|