AM186ES Advanced Micro Devices, AM186ES Datasheet - Page 135

• Manufacturer Part Number: AM186ES
• Description: microcontrollers provide a low-cost/ high-performance solution for embedded system designers who wish to use the x86 architecture.
• Manufacturer: Advanced Micro Devices

9.3
9.3.1
Figure 9-2
PROGRAMMABLE DMA REGISTERS
The following sections describe the control registers that are used to configure and operate
the two DMA channels.
DMA Control Registers
(D0CON, Offset CAh, D1CON, Offset DAh)
The DMA control registers (see Figure 9-2) determine the mode of operation for the DMA
channels. These registers specify the following options:
The DMA channel control registers can be changed while the channel is operating. Any
changes made during DMA operations affect the current DMA transfer.
DMA Control Registers
The value of D0CON and D1CON at reset is undefined except ST is set to 0.
Bit 15: Destination Address Space Select (DM/IO)—Selects memory or I/O space for
the destination address. When DM/IO is set to 1, the destination address is in memory
space. When set to 0, the destination address is in I/O space.
Bit 14: Destination Decrement (DDEC)—When DDEC is set to 1, the destination address
is automatically decremented after each transfer. The address decrements by 1 or 2
depending on the byte/word bit (B/W, bit 0). The address remains constant if the increment
and decrement bits are set to the same value (00b or 11b).
Whether the destination address is memory or I/O space
Whether the destination address is incremented, decremented, or maintained constant
after each transfer
Whether the source address is memory or I/O space
Whether the source address is incremented, decremented, or maintained constant after
each transfer
If DMA activity ceases after a programmed number of DMA cycles
If an interrupt is generated with the last transfer
The mode of synchronization
The relative priority of the DMA channel with respect to the other DMA channel
Whether timer 2 DMA requests are enabled or disabled
Whether bytes or words are transferred (on the Am186 microcontroller only)
Whether the DRQ pin is used for external interrupts
DM/IO
15
DDEC
DINC
SM/IO
SDEC
SINC
DMA Controller
TC
INT
SYN1/SYN0
7
P
TDRQ
EXT
CHG
ST
0
B/W
9-3