| 摘要 |
<p>PURPOSE:To prevent the erroneous writing of unaimed data by making a program control circuit which outputs a write start instruction to execute a program only when the circuit detects a prescribed number of clocks required for issuing a program instruction. CONSTITUTION:A program control circuit 1 outputs a write start signal PGCY upon detecting the falling trigger of a chip select signal CS in an enable state. A clock number detection circuit 2 sets a signal KCOUNT to 'H' and the control circuit 1 to an enable state only when 16 pieces of clock signals which are required for a program are inputted. When the signal CS falls while the control circuit 1 is set to the enable state, the signal PGCY of the circuit 1 rises and the circuit 1 starts writing. However, when the number of inputted clock signals is not 16, but 17 or 15, the signal KCOUNT is 'L' and the signal PGCY does not rise. As a result, the circuit 1 is set to a write inhibit state. Therefore, the erroneous writing of unaimed data is inhibited.</p> |
