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Intel386™ EX EMBEDDED MICROPROCESSOR USER’S MANUAL
12-14
transfer is suspended and the channel waits for the request input to be
reactivated before it continues.
12.2.7.1 Single Data-transfer Mode
In single data-transfer mode, a DMA request causes the channel to gain bus control. The channel
transfers data (a byte or a word), decrements the buffer byte count (by 1 for byte transfers and 2
for word transfers), then relinquishes bus control. The channel will then Autoinitialize if it has
been programmed to do so. The channel continues to operate in this manner until the buffer trans-
fer is complete or terminated. In this mode, the channel gives up bus control after every data trans-
fer and must regain bus control (through priority arbitration) before every data transfer. The
channel’s buffer-transfer mode determines whether the channel becomes idle or is reprogrammed
after a buffer transfer completes or is terminated.
The single data-transfer mode is compatible with all of the buffer-transfer modes. The following
flowcharts show the transfer process flow for a channel programmed for single data-transfer
mode with each buffer-transfer mode: single (Figure 12-8), autoinitialize (Figure 12-9), and
chaining (Figure 12-10).