Specifications

DMA Controller (V40)
Count Register
The Count register includes a 16-bit base count and a 16-bit current
count. The base count and current count are programmed with the
number of bytes to be transferred by the DMA operation. The base
count remains the same until a new count is specified. If the auto-
initialize feature is used, the base count is transferred to the current
count when the count register is decremented to zero and the last
DMA operation is complete. The current count register is
decremented by one after each transfer to indicate the number of bytes
not yet transferred.
Count
Adjuster
The Count Adjuster automatically updates the current count register
each time a data transfer is completed. The Count register is
incremented or decremented by one for each byte transfer.
Control
Registers
The Control register functional block consists of six registers that are
used to control the DCU operation and provide DCU status. The
registers are explained in the following section.
9-6