| 摘要 |
PURPOSE:To easily prepare a test pattern in which tests on input and output levels can be performed surely by separating an internal circuit from an input- output circuit and outputting the output value of an input buffer to the outside of a semiconductor integrated circuit by means of a control signal from the outside of the integrated circuit. CONSTITUTION:At the time of testing, an input-output circuit and internal bus 6 are separated from each other and outputs of AND circuits 8 and 16 are fixed to '0'. In addition, a read signal READ and write signal WRITE are invalidated. Moreover, since a port mode signal is set to '1' for resetting, the input and output states of an external terminal 1 are decided by an OUT signal. When data are inputted from the external terminal 1 and the OUT signal is set to '0', the output of an input buffer 2 is decided and the data are latched in a port register 4. When the OUT signal is set to '1' thereafter, the data are outputted to the terminal 1 through an output buffer 3. Therefore, the input-output level of a circuit, the peripheral function terminal of which is multiplexed to a port, or a user circuit can be tested easily and surely. |
