Specifications

DMA Controller (V40)

DMA Initialize Command (DICM)

The initialization command, shown in Figure 9-2, includes one bit

that can be set to a logical 1 to reset the DCU. This register must be

written to with the byte output instruction.

Address:Base + 0

Access:Write Only

76543210

RES

Reset

0 No reset

1 Reset

0——————

Figure 9–2. DMA Initialization Command Register.

DMA Channel

(DCH)

The DMA Channel register, shown in Figure 9-3, must be accessed

with byte output and input instructions. The DCH register has a

different format for read and write operations. For the write operation,

the BASE bit is used to select between the base and current register

groups for both the address and count. Both base and current registers

are written or only the current register is read if BASE is first

programmed with a logical 0. Programming BASE with a logical 1

selects the base to be read or written to.

9-8