| 摘要 |
PROBLEM TO BE SOLVED: To realize a first-in first-out(FIFO) memory having a multi-port memory accessed for read-out/write-in operation by activating a selected read-out/ write-in word line without using a counter. SOLUTION: The write-in word line is successively activated by a single bit (e.g. bit of '1') to circulate a write-in pointer shift register 204. Relating to a read-out pointer, a coincidence circuit consisting of transistors 207-210 and an inverter 211 looks ahead a row of memory cell, and compares the present position of the read-out pointer with the present position of the write-in pointer. When they agree, it shows that the read-out pointer advances to the row (m-1) adjacent to the row of the write-in pointer (m), and thus, the line 216 transits from high (high potential) to low (low potential), and this transition is conducted to an output latch circuit 217, and an empty flag EF is set. |
