DMA transfer control device
A DMA transfer control device comprises: a DMA arbiter that performs DMA transfer for each DMA channel formed by a combination of a memory and a plurality of input/output devices and DMA controller circuits that control the DMA arbiter; a judgment unit and a transfer time calculation unit that calculates a next DMA transfer scheduled time based on the DMA transfer size for a DMA transfer request and a judgment time. A timer counter that times the judgment time at a unit time interval, and a comparator that compares the judgment time at which a DMA transfer request arrives with the DMA transfer scheduled time are also provided, and the judgment unit sends the DMA transfer permission to the DMA arbiter when an output of the comparator indicates that the judgment time is not earlier than the DMA transfer scheduled time. The efficiency of data transfer by dynamically controlling DMA transfer is performed.
1. A Direct Memory Access (DMA) transfer control device, comprising:
a DMA arbiter that performs DMA transfer for each DMA channel formed by a combination of a memory and a plurality of input/output devices; and
a DMA controller circuit that controls the DMA arbiter;
a judgment unit that sends a DMA transfer permission to said DMA arbiter in a case where a judgment time at which a DMA transfer request arrives from said input/output device is not earlier than a DMA transfer scheduled time;
a timer counter that times said judgment time at a unit time interval; and
a comparator that compares said judgment time at which said DMA transfer request arrives with said DMA transfer scheduled time; wherein
said judgment unit sends the DMA transfer permission to said DMA arbiter when an output of said comparator indicates that said judgment time is not earlier than said DMA transfer scheduled time and does not send the DMA transfer permission to said DMA arbiter when the output of said comparator indicates that said judgment time is earlier than said DMA transfer scheduled time; and
a transfer time calculation unit that calculates a next round of said DMA transfer scheduled time based on a DMA transfer size for said DMA transfer request and said judgment time.
2. A Direct Memory Access (DMA) transfer control device, comprising:
a DMA arbiter that performs DMA transfer for each DMA channel formed by a combination of a memory and a plurality of input/output devices; and
a DMA controller circuit that controls the DMA arbiter;
a judgment unit that sends a DMA transfer permission to said DMA arbiter in a case where a judgment time at which a DMA transfer request arrives from said input/output device is not earlier than a DMA transfer scheduled time; and
a transfer time calculation unit that calculates a next round of said DMA transfer scheduled time based on a DMA transfer size for said DMA transfer request and said judgment time,
wherein
said transfer time calculation unit comprises a calculation unit that multiplies a set value of a DMA transfer size for said DMA transfer request by a set value of a DMA transfer interval for unit DMA transfer size to create a multiplication result, and that adds said judgment time to the multiplication result; and
a register that holds the calculation result of said calculation unit as a next round of said DMA transfer scheduled time.
3. A system comprising:
a direct memory access (DMA) arbiter configured to perform a DMA transfer in response to a DMA transfer request from an input/output device;
a calculation unit configured to calculate a DMA transfer scheduled time based on a multiplication result of a DMA transfer size of the DMA transfer request and a DMA transfer interval for a unit DMA transfer size when, the DMA transfer request is permitted; and
a judgment unit coupled between the input/output device and the DMA arbiter to reject another DMA transfer request from the input/output device when the another DMA transfer request arrives earlier than a DMA transfer scheduled time.