Communication dma device

Details Communication dma device Communication dma device

G - Physics

06

F

G06F 13/00 (2006.01) G06F 13/28 (2006.01)

Patent

CA 2289192

A communication DMA device having temporary storage for temporarily storing data to be transferred and an output for outputting several bits of data simultaneously is disclosed. The DMA device also has a register for storing information indicating an area of the memory in which data to be transmitted is stored, the capacity of the data to be transmitted, and an indication of the start of communication. A bus switching request requests the CPU to release the data bus, allowing the data, having a prescribed bit width, to be read from memory. The switching request circuit immediately reconnects the data bus to the CPU after termination of the data transfer. Based on the information stored in the register means, the data read from memory via the data bus is temporarily stored in a temporary storage circuit. The temporarily stored data is divided into several units, such as 8 bit units, which are output serially via the communication circuit. The communication DMA device frees the CPU from the data bus and performs communication control and transmission of data, thereby reducing CPU load and also allowing high-speed data transfer.

Selon l'invention, lorsqu'un bus de données est séparé d'une unité centrale (1) et qu'un signal prêt pour la transmission (TXRDY) devient actif, un circuit de commande DMA (10) lit collectivement des données de 32 bits selon une première adresse d'une mémoire DRAM (2) où les données sont stockées et une largeur d'adresse qui sont fixées par l'unité centrale (1), puis mémorise les données dans une mémoire tampon de transmission (16). Ensuite, un sélecteur (17) sélectionne les données en unités de 8 bits à partir de la mémoire tampon de transmission (16) et alors un sélecteur (17) écrit les données sélectionnées dans un circuit de communication (14), après quoi la demande de libération de bus est annulée. Lorsqu'un signal prêt pour la transmission est reçu de nouveau, le même traitement est effectué.

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