| 摘要 |
<p>PURPOSE:To lessen the number of times of writing by checking rewriting of the same data on the occasion of writing in EEPROM. CONSTITUTION:In response to a write request from another host, an R/W control circuit 2 sets E<2>PROM 1 in a read modify mode, makes *CS (chip select signal) active and sets a read cycle. Addresses A0 to A7 to be written are inputted to the E<2>PROM 1. Thereby a read register 3 is made to hold data D0 to D7 at the time of the read cycle. A comparator circuit 4 compares these data with data WD0 to WD7 to be written. Only when they are not coincident, the R/W control circuit 2 makes a signal *WE in the next write cycle and writing is made in the E<2>PROM 1. In the case when they are coincident, *WE is not made active and the writing in the E<2>PROM is stopped. Accordingly, no rewriting of the same data is executed and thus the number of times of writing of data can be lessened to the necessary minimum.</p> |
