At speed TAP, dual port router, and command flip-flop circuitry
This disclosure describes different ways to improve the operation of a device's 1149.1 TAP to where the TAP can perform at-speed Update & Capture, Shift & Capture and Back to Back Capture & Shift operations. In a first embodiment of the disclosure the at-speed operations are achieved by time division multiplexing CMD signals onto the TMS input to the TAP. The CMD signals are input to a CMD circuit that operates in conjunction with a Dual Port Router to execute the at-speed operations of a circuit. In a second embodiment of the disclosure the at-speed operations are achieved by detecting the TAP's Exit1DR state as a CMD signal that is input to the CMD circuit that operates in conjunction with a Dual Port Router to execute the at-speed operations of a circuit. In a third embodiment of the disclosure the at-speed operations are achieved by detecting the TAP's Exit1DR and PauseDR states and in response producing Capture and Update signals that are input to a Programmable Switch that operates in conjunction with a Dual Port Router to execute the at-speed operations of a circuit. In a fourth embodiment of the disclosure the at-speed operations are achieved by detecting the TAP's Exit1DR and PauseDR states and inputting these states to a Dual Port Router to control the at-speed operations of a circuit. Each of the embodiments may be augmented to include externally accessible Update and Capture input signals that can be selected to allow a tester to directly control the at-speed operations of a circuit. The improvements of the disclosure are achieved without requiring any additional IC pins beyond the 4 required TAP pins, except for examples showing use of additional data input pins (TDI or WPI signals), additional data output pins (TDO or WPO signals) or examples showing use of additional control input pins (Capture and Update signals). Devices including the TAP improvements can be operated compliantly in a daisy-chain arrangement with devices that don't include the TAP improvements.
1. An integrated circuit comprising:
A. a test clock lead and a test mode select lead;
B. a state machine having a test clock input coupled to the test clock lead, a test mode select input coupled to the test mode select lead, and data register control outputs;
C. command flip flop circuitry having a clock input coupled to the test clock lead, an input coupled to the test mode select lead, and a command flip flop circuitry output; and
D. dual port router circuitry having state machine inputs connected to the data register control outputs, another input connected to the command flip flop circuitry output, a data register enable input, and data register outputs.
2. The integrated circuit of claim 1 including a test data in lead and an instruction register having an input coupled to the test data in lead an enable output connected to the data register enable input.
3. The integrated circuit of claim 1 including a test data in lead and a data register having an input coupled to the a test data in lead and data register control inputs connected to the data register outputs.
4. The integrated circuit of claim 1 in which the state machine has states of Test Logic Reset, Run Test/Idle, SelectDR, and SelectIR.