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 E2PROM 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 E2PROM 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 E2PROM 1. In the case when they are coincident, *WE is not made active and the writing in the E2PROM 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.
WAKABAYASHI MASAMI
TAKAHASHI KAZUNORI
IIJIMA HIROSHIGE
TAKAHAGI HIROSHI
KUNII NOBUTAKA
