RECEPTION FRAME TRANSFER SYSTEM AND COMMUNICATION CONTROLLER

PURPOSE:To successively continue normal communication control even if it comes to a state where a data part is insufficient by storing the header part of a reception frame and the data part in reception buffer groups which are provided for plural sets by means of dividing them. CONSTITUTION:The length of the header part of the frame to be received is stored in the reception buffer length 803 of a buffer control register 81 and the maximum length of the data part in the buffer length of a register 82 as a condition before the transfer of the reception frame. When a DMA controller 2 receives a DMA start request from a frame reception circuit in a DMA stop state, it decides the free conditions of the buffer group 61. When the free buffer does not exist, a DMA action is terminated by assuming it to be the occurrence of the overrun of the reception buffer. When there is the free buffer, a descripter read pointer 802 is updated and the reception frame is DMA transferred to the free buffer.