Appeal No. 1998-1114
Application 08/353,254
BACKGROUND
The disclosed invention is directed to a semiconductor
memory incorporating a protecting circuit to prevent data
stored in a memory portion from being read out and illegally
copied. The protecting circuit is shown in figure 3. Memory
portion 1 is blocked from being read out to a terminal 11 by a
three-state buffer 4a. Key release data is input to input
register 25 via terminal 11 when the three-state buffer is in
a high-impedance state. When the key release data matches
stored key data in key memory 24, the flip-flop 22 is set
which cancels the high-impedance state of the buffer 4a and
allows data to be read.
Claim 13 is reproduced below.
13. A semiconductor memory apparatus, comprising:
a memory portion storing a program;
a terminal for external connection;
a three-state buffer, one end of said three-state
buffer is connected to said memory portion so that said
three-state buffer can receive program data from said
memory portion, and another end of said three-state
buffer is connected to said terminal for external
connection, said three-state buffer being capable of
taking a high-impedance state in addition to two-value
states of high-level and low-level;
a key memory for storing key data;
- 3 -
Page: Previous 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Next
Last modified: November 3, 2007