| 摘要 |
<p>PURPOSE:To perform high-speed data transfer between an external and an internal memory, by adding the function of inputting and outputting external data from and to the internal memory without the intervention of an internal register. CONSTITUTION:When an internal memory direct memory access request signal (IMDMA request signal) 41 to be supplied from the outside to a READ and WRITE signal generating circuit in a microcomputer, input/output buffer of an address bus, etc., is activated, tristate buffers 28 and 29 which almost an READ and an WRITE output signal are closed to invalidate the READ and WRITE output signals, and an READ and an WRITE signal line are controlled by external inputs. On the other hand, the outputs of 3-input AND gates 30 and 32 are made inactive because the IMDMA request signal 41 is activated and the outputs of 2-input OR gates 34 and 35 are determined by the outputs of 2-input AND gates 31 and 33.</p> |
