rej05b0061_m16cap| Application Note
APPLICATION NOTE M16C/62A Group
Operation of DMAC (one-shot transfer mode)
1.0 Abstract
In one-shot transfer mode, choose functions from the items shown in Table 1. Operations of the circled items are described below. Table 1. Choosed functions
Item Transfer space O Set-up Fixed address from an arbitrary 1 M bytes space Arbitrary 1 M bytes space from a fixed address Fixed address from fixed address Unit of transfer O 8 bits 16 bits
2.0 Introduction
Operation (1) When software trigger is selected, setting software DMA request bit to "1" generates a DMA transfer request signal. (2) If DMAC is active, data transfer starts, and the contents of the address indicated by the DMAi forward-direction address pointer are transferred to the address indicated by the DMAi destination pointer. When data transfer starts directly after DMAC becomes active, the value of the DMAi transfer counter reload register is reloaded to the DMAi transfer counter, and the value of the DMAi source pointer is reloaded by the DMAi forward-direction address pointer. Each time a DMA transfer request signal is generated, 1 byte of data is transferred. The DMAi transfer counter is down counted, and the DMAi forward-direction address pointer is up counted. (3) If the DMA transfer counter underflows, the DMA enable bit changes to "0" and DMA transfer is completed. The DMA interrupt request bit changes to "1" simultaneously. Figure 1 shows an example of operation
(1) Request signal for a DMA transfer occurs (2) Data transfer begins BCLK Destination Address bus CPU use Source Dummy cycle CPU use Source
(3) Underflow
Destination Dummy cycle CPU use
RD signal
WR signal Destination Data bus Write signal to software DMAi request bit DMAi request bit CPU use Source Dummy cycle CPU use Source Destination Dummy cycle
CPU use
DMA transfer counter
Indeterminate 0116
0016
FF16
DMAi interrupt request bit DMAi enable bit
Cleared to "0" when interrupt request is accepted, or cleared by software In the case in which the number of transfer times is set to 2.
Figure 1. Example of operation of one-shot transfer mode
REJ05B0061-0100Z
May 2003
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