Circuits and methods for processing memory redundancy data
View Patent ↗An interface processes memory redundancy data on an application specific integrated circuit (ASIC) with self-repairing random access memory (RAM) devices. The interface includes a state machine, a counter, and an array of registers. The state machine is coupled to a redundancy chain. The redundancy chain includes coupled redundant elements of respective memory elements on the ASIC. In a shift-in mode, the interface shifts data from each of the elements in the redundancy chain and compresses the data in the array of registers. The interface communicates with a test access port coupled to one or more eFuse devices to store and retrieve the compressed data. In a shift-out mode, the interface decompresses the data stored in the array of registers and shifts the decompressed data to each unit in the redundancy chain. The interface functions absent knowledge of the number, bit size and type of self-repairing RAM devices in the redundancy chain.
1. A method for processing memory redundancy data, the method comprising:
coupling serial-shift registers associated with respective redundant memory elements included in self-repairing random access memory devices on an application specific integrated circuit (ASIC) to form a redundancy chain;
reading memory redundancy data from the serial-shift registers of the self-repairing random access memory devices of the redundancy chain;
compressing the memory redundancy data in an interface coupled to the redundancy chain, a core logic and a test access port (TAP) on the ASIC, wherein compressing comprises a step-wise comparison of information in the memory redundancy data, the step-wise comparison responsive to an indication that a bit-slice in a particular location in the redundancy chain has been replaced by a redundant memory element;
in a first mode of operation, storing the compressed memory redundancy data in an array of volatile memory elements in the interface coupled to the redundancy chain;
coupling an eFuse device to the TAP; and
in a second mode of operation, communicating the compressed memory redundancy data from the volatile memory elements in the interface to the eFuse device via the TAP for storage in the eFuse device;
subsequent to the communicating, downloading the compressed memory redundancy data stored in the eFuse device by communicating the same to the interface via the TAP, storing the compressed memory redundancy data in the interface, and using the interface to decompress and shift the memory redundancy data through the serial-shift registers of the redundancy chain.
2. The method of claim 1 , wherein reading memory redundancy data from the serial-shift registers of the self-repairing random access memory devices of the redundancy chain is performed after a built-in self test procedure at the completion of which the redundancy chain contains memory redundancy data that enables each self-repairing random access memory device to pass a test.
3. The method of claim 1 , wherein compressing the memory redundancy data comprises enabling a counter.
4. The method of claim 3 , wherein compressing the memory redundancy data comprises, operating a state machine that updates the counter and identifies when a first data value is present in the memory redundancy data.
5. The method of claim 1 , wherein storing the compressed memory redundancy data in the interface comprises using an array of storage registers responsive to a pointer input, a data input and a present count.
6. The method of claim 5 , wherein when a first instance of a first data value is present in the memory redundancy data the present count is stored in a first row of associated storage registers and the pointer is incremented.
7. The method of claim 6 , wherein when a second instance of the first data value is present in the memory redundancy data the present count is stored in a second row of associated storage registers and the pointer is incremented.
8. The method of claim 1 , wherein communicating the compressed memory redundancy data from the interface to the eFuse device via the TAP comprises directing the TAP to program the memory redundancy data in a set of eFuse elements.
9. The method of claim 1 , further comprising:
identifying from the memory redundancy data an end of the redundancy chain.
10. An interface for processing memory redundancy data on an application specific integrated circuit (ASIC) with self-repairing random access memory elements, the interface comprising:
a state machine having a data input and a data output coupled to a redundancy chain, the redundancy chain including coupled redundant elements of respective random access memory elements on the ASIC, the state machine configured to generate a first control signal, a second control signal, and a third control signal;
an interface counter arranged to receive the first control signal and generate a present count; and
an array of registers operating in a single clock domain and indirectly coupled to a non-volatile storage element through a test access port interface, the array of registers arranged to receive and store a bit in the array of registers in response to the present count, the second control signal and the third control signal, wherein the third control signal is communicated to the array of registers via a decoder.
11. The interface of claim 10 , wherein the second control signal identifies when a received bit from the redundancy chain is a first logic value.
12. The interface of claim 10 ,
wherein an output from the decoder selects a row in the array of registers in accordance with the third control signal when the interface is operating in a shift-in mode.
13. The interface of claim 10 , further comprising:
a first multiplexer coupled to the array of registers, the first multiplexer arranged to select a row in the array of registers in accordance with the third control signal when the interface is operating a shift-out mode.
14. The interface of claim 13 , further comprising:
a redundancy data controller comprising a comparator and a second multiplexer, the comparator arranged to receive a present count value and a select output of the array of registers from the first multiplexer and generate a comparator output that identifies when the present count value and the select output of the array of registers match, the second multiplexer receiving a data signal from the state machine at a first input and the comparator output at a second input, the second multiplexer forwarding one of the first input and the comparator output in accordance with the data enable signal from the state machine.
15. The interface of claim 10 , further comprising:
a detector coupled to the data input, the detector arranged to identify the end of redundancy data from the redundancy chain by forwarding a detection signal to the state machine.
16. The interface of claim 15 , wherein the detector is responsive to a series of P consecutive bits each having the first logic value where P is an integer value.
17. The interface of claim 10 , the state machine generating a fourth control signal and a fifth control signal that are distributed to respective inputs of each self-repairing random access memory element in the redundancy chain.
18. The interface of claim 17 , wherein the fourth control signal directs each self-repairing random access memory element in the redundancy chain to select an external clock that is different from a nominal memory clock.
19. The interface of claim 17 , wherein the fifth control signal directs each self-repairing random access memory element in the redundancy chain to shift one bit.
20. The interface of claim 10 , wherein the state machine comprises an asynchronous test access port bus for communicating commands to an eFuse element coupled to the test access port.