Programmable pin configuration logic circuit for providing a chip select signal and related method
First Claim
1. A programmable pin configuration logic circuit for providing a chip select signal, comprising:
- a programmable pin function register including a first bit field defining a selected chip select pin function of a plurality of chip select pin functions to be provided as the chip select signal;
a first obey logic circuit having a first input for receiving a first cycle start signal, a second input for receiving a first cycle end signal, and an output for providing a first obey signal, said first obey logic circuit activating said first obey signal in response to said first cycle start signal and deactivating said first obey signal in response to said first cycle end signal;
a second obey logic circuit having a first input for receiving a second cycle start signal, a second input for receiving a second cycle end signal, and an output for providing a second obey signal, said second obey logic circuit activating said second obey signal in response to said second cycle start signal and deactivating said second obey signal in response to said second cycle end signal;
a plurality of pin function logic circuits each associated with a corresponding one of said plurality of chip select pin functions;
each pin function logic circuit having first and second control inputs respectively receiving said first and second obey signals, first and second timing inputs receiving first and second timing signals, corresponding to first and second memory access cycles, respectively, and associated with said selected chip select pin function, and an output providing a function output signal;
each pin function logic circuit activating said function output signal thereof in response to said first timing signal when said first obey signal is active and to said second timing signal when said second obey signal is active, when said first bit field selects said corresponding one of said plurality of chip select pin functions; and
an output circuit having a plurality of inputs for receiving said function output signal from each of said plurality of pin function logic circuits, and an output for providing the chip select signal, said output circuit activating the chip select signal in response to an activation of said function output signal of one of said plurality of pin function logic circuits.
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Accused Products
Abstract
A pin configuration logic circuit (120) has a pin function register (130) which defines a selected pin function, such as chip enable, write enable, and output enable, to be provided as a chip select signal. The logic circuit (120) allows an arbitrary pipeline length by causing the chip select signal to obey only the timing of the active cycle. For a two-deep access pipeline, the logic circuit (120) marks whether a first or a second cycle owns the pin. The pin configuration logic circuit (120) uses the timing associated with the selected pin function to provide the chip select signal during the first cycle if the attributes of the cycle, such as an access to a region programmed in the pin function register, are met. During the second cycle, the pin configuration logic circuit (120) further obeys the timing associated with the selected pin function if the attributes of that cycle are also met.
35 Citations
14 Claims
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1. A programmable pin configuration logic circuit for providing a chip select signal, comprising:
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a programmable pin function register including a first bit field defining a selected chip select pin function of a plurality of chip select pin functions to be provided as the chip select signal; a first obey logic circuit having a first input for receiving a first cycle start signal, a second input for receiving a first cycle end signal, and an output for providing a first obey signal, said first obey logic circuit activating said first obey signal in response to said first cycle start signal and deactivating said first obey signal in response to said first cycle end signal; a second obey logic circuit having a first input for receiving a second cycle start signal, a second input for receiving a second cycle end signal, and an output for providing a second obey signal, said second obey logic circuit activating said second obey signal in response to said second cycle start signal and deactivating said second obey signal in response to said second cycle end signal; a plurality of pin function logic circuits each associated with a corresponding one of said plurality of chip select pin functions; each pin function logic circuit having first and second control inputs respectively receiving said first and second obey signals, first and second timing inputs receiving first and second timing signals, corresponding to first and second memory access cycles, respectively, and associated with said selected chip select pin function, and an output providing a function output signal; each pin function logic circuit activating said function output signal thereof in response to said first timing signal when said first obey signal is active and to said second timing signal when said second obey signal is active, when said first bit field selects said corresponding one of said plurality of chip select pin functions; and an output circuit having a plurality of inputs for receiving said function output signal from each of said plurality of pin function logic circuits, and an output for providing the chip select signal, said output circuit activating the chip select signal in response to an activation of said function output signal of one of said plurality of pin function logic circuits. - View Dependent Claims (2, 3, 4, 5)
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6. A programmable pin configuration logic circuit for providing a chip select signal, comprising:
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a programmable pin function register including a bit field defining a selected chip select pin function of a plurality of chip select pin functions; obey logic means, coupled to said programmable pin function register, for activating a first obey signal during a first pipelined cycle and a second obey signal during a second pipelined cycle; and pin function output means coupled to said programmable pin function register and to said obey logic means, for activating the chip select signal in response to one of a first plurality of input timing signals corresponding to said selected chip select pin function if said first obey signal is active, and for activating the chip select signal in response to one of a second plurality of input timing signals corresponding to said selected chip select pin function if said second obey signal is active. - View Dependent Claims (7, 8, 9, 10)
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11. A method for providing a chip select signal, comprising the steps of:
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defining a selected chip select pin function of a plurality of chip select pin functions; activating a first obey signal during a first pipelined cycle; activating a second obey signal during a second pipelined cycle; activating the chip select signal in response to one of a first plurality of input timing signals corresponding to said selected chip select pin function if said first obey signal is active; and activating the chip select signal in response to one of a second plurality of input timing signals corresponding to said selected chip select pin function if said second obey signal is active. - View Dependent Claims (12, 13, 14)
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Specification