| 摘要 |
PURPOSE: A method for accessing a single mode direct memory using a central processing unit(CPU) is provided to designate a bank of a CPU by separating an access of the CPU or an access of a direct memory access controller in case of transmitting/receiving an external device supporting a signal mode direct memory access transmission. CONSTITUTION: It is detected whether a direct memory access demanding signal(nXDREQ) of an external device for supporting a signal mode direct memory access transmission exists. If the direct memory access demanding signal(nXDREQ) exists, one bank out of banks which are not used by a system in a CPU is allocated as a virtual bank, and a control register is set by a predetermined value for minimizing an access time in the allocated virtual bank, and a direct memory access transmission is performed. A memory controller(2) outputs each control signal(nRAS, nCAS, nOE) by the CPU and controls a D-RAM(1). If a direct memory access demanding signal is applied, a direct memory access controller(3) controls the memory controller(2) and performs a direct memory access transmission. A video display processor(4) performs a signal process of a video signal and outputs the direct memory access demanding signal(nXDREQ) for the direct memory access transmission.
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