| 摘要 |
PURPOSE:To obtain a device having a code-information containing function, handling thereof is convenient, by utilizing one part of a nonerasable EPROM as a containing section for product code-informations. CONSTITUTION:A control circuit WCON discriminates a voltage level fed from an external terminal Vpp, and transmits the control of writing/reading operating modes and the writing high voltage over an EPROM. When comparatively low voltage such as internal supply voltage Vcc is fed from the external terminal Vpp, a discriminating signal at a low level is formed by a built-in voltage-level detecting circuit. The signal is utilized for shaping a reading operating mode when the EPROM is selected by a CPU. When high voltage for the writing of the EPROM is fed from the external terminal Vpp, on the other hand, a discriminating signal at a high level is formed by the voltage level detecting circuit. The signal brings a data input buffer for the EPROM to the state of operation while it processes and shapes a writing high-level signal from a logic ''0'' shaped by using high voltage Vpp and writes the signal to a memory cell. |
