Built-in self-test circuit applied to high speed I/O port
View Patent ↗A built-in self-test circuit (BIST) applied to a high speed I/O port is provided. The BIST circuit includes a detecting unit, a flag unit and a selecting unit. The detecting unit has a first input terminal for receiving a serial output signal, a second input terminal for receiving a serial enable signal, and an output terminal for generating a detection signal. The flag unit receives the detection signal and generates a flag signal. The selecting unit receives the serial output signal, the serial enable signal and the flag signal. When a reset signal is at a first level, the selecting unit transmits the serial output signal and the serial enable signal to the I/O port. When the reset signal is at a second level, the serial output signal and the serial enable signal possesses a predetermined relationship.
1. A built-in self-test (BIST) circuit for a memory controller, the memory controller comprising a core circuit and an I/O port, the core circuit outputting a reset signal, a serial output signal and a serial enable signal, the I/O port comprising an output driver, the BIST circuit comprising:
a detecting unit, having a first input terminal for receiving the serial output signal, a second input terminal for receiving the serial enable signal, and an output terminal for generating a detection signal
a flag unit, for receiving the detection signal to generate a flag signal; and
a selecting unit, for receiving the serial output signal, the serial enable signal and the flag signal;
wherein, when the reset signal is at a first level, the selecting unit transmits the serial output signal and the serial enable signal to an input terminal and an enable terminal of the output driver, respectively; when the reset signal is at a second level, the serial output signal and the serial enable signal possesses a predetermined relationship, and the selecting unit transmits the flag signal to the input terminal of the output driver.
2. The BIST circuit according to claim 1 , wherein before the serial output signal and the serial enable signal possesses a predetermined relationship, the detecting unit sets the flag signal in the flag unit.
3. The BIST circuit according to claim 1 , wherein the selecting unit comprises:
a first multiplexer, having a 0 input terminal for receiving the serial output signal, a 1 input terminal for receiving the flag signal, and a selecting terminal for receiving an inverted reset signal; and
a second multiplexer, having a 0 input terminal for receiving the serial enable signal, a 1 input terminal for receiving a control signal, and a selecting terminal for receiving the inverted reset signal;
wherein, the first level of the reset signal is a high level, the second level of the reset signal is a low level, and the control signal is capable of enabling the output driver.
4. The BIST circuit according to claim 1 , wherein the first level of the reset signal is a high level, the second level of the reset signal is a low level, and the predetermined relationship between the serial output signal and the serial enable signal is a complementary relationship.
5. The BIST circuit according to claim 4 , wherein the detecting unit comprises:
a first NOR gate, having a first input terminal for receiving the serial output signal, and a second input terminal for receiving the reset signal;
a second NOR gate, having a first input terminal for receiving the serial enable signal, and a second input terminal for receiving the reset signal;
an XOR gate, having two input terminals respectively connected to an output terminal of the first NOR gate and the second NOR gate;
a delay unit, for receiving the reset signal and generating a delayed reset signal; and
an OR gate, having a first input terminal for receiving the delayed reset signal, a second input terminal connected to the output terminal of the XOR gate, and an output terminal for generating the detection signal.
6. The BIST circuit according to claim 5 , wherein the flag unit comprises:
a first NAND gate, having a first input terminal for receiving the detection signal, a second input terminal and an output terminal for generating the flag signal; and
a second NAND gate, having a first input terminal for receiving the inverted reset signal, a second input terminal connected to the output terminal of the first NAND gate, and an output terminal connected to the second input terminal of the first NAND gate.
7. The BIST circuit according to claim 1 , wherein the core circuit comprises:
a control unit, for outputting a parallel output signal and a parallel enable signal;
an output signal parallel-to-serial converter, for receiving the parallel output signal and outputting the serial output signal; and
an enable signal parallel-to-serial converter, for receiving the parallel enable signal and outputting the serial enable signal.
8. The BIST circuit according to claim 1 , wherein the I/O port comprises:
an I/O pad, connected to an output terminal of the output driver; and
an input driver, having an input terminal connected to the I/O pad.
9. A BIST circuit for a memory controller, the memory controller comprising a core circuit, a first I/O port and a second I/O port, the core circuit outputting a reset signal, a first output signal and a second output signal, the first I/O port receiving the first output signal and outputting the output signal, the second I/O port receiving the second output signal and outputting the second output signal, the BIST circuit comprising:
a detecting unit, having a first input terminal connected to the first I/O port to receive the first output signal, a second input terminal connected to the second I/O to receive the second output signal, and an output terminal for generating a detection signal; and
a flag unit, for receiving the detection signal and generating a flag signal;
wherein, when the reset signal is at a first level, the flag signal is cleared; when the reset signal is at a second level, the serial output signal and the serial enable signal possesses a predetermined relationship, and the detecting unit sets the flag signal in the flag unit before the predetermined relationship is present.
10. The BIST circuit according to claim 9 , wherein the first level of the reset signal is a high level, the second level of the reset signal is a low level, and the predetermined relationship is a complementary relationship.
11. The BIST circuit according to claim 10 , wherein the detecting unit comprises:
a first NOR gate, having a first input terminal for receiving the serial output signal, and a second input terminal for receiving the reset signal;
a second NOR gate, having a first input terminal for receiving the serial enable signal, and a second input terminal for receiving the reset signal;
an XOR gate, having two input terminals respectively connected to an output terminal of the first NOR gate and the second NOR gate;
a delay unit, for receiving the reset signal and generating a delayed reset signal; and
an OR gate, having a first input terminal for receiving the delayed reset signal, a second input terminal connected to an output terminal of the XOR gate, and an output terminal for generating the detection signal.
12. The BIST circuit according to claim 11 , wherein the flag unit comprises:
a first NAND gate, having a first input terminal for receiving the detection signal, a second input terminal and an output terminal; and
a second NAND gate, having a first input terminal for receiving the inverted reset signal, a second input terminal connected to the output terminal of the first NAND gate and for generating the flag signal, and an output terminal connected to the second input terminal of the first NAND gate.
13. The BIST circuit according to claim 9 , wherein the first I/O port comprises:
an output driver, having an input terminal for receiving the first output signal;
an I/O pad, connected to an output terminal of the output driver; and
an input driver, having an input terminal connected to the I/O pad to output the first output signal.