07KT98 GJR5253100R3160模块，ABB数据库
DMAC启动模式DMAC有两种启动模式：直接启动和命令启动链接（分散-聚集）。
在直接模式下，数据地址指针和字节计数为加载到芯片中。
在命令链接模式下，数据地址和字节的表计数放在本地RAM中，并加载表的地址进入芯片。芯片遍历地址和字节计数从本地RAM移动每个数据块，如桌子命令支持分散-聚集操作链接。
07KT98 GJR5253100R3160模块PCC可以DMA到/从本地DRAM和VMEbus内存只有任何其他访问都会导致本地总线超时。DMAC运行状态DMAC始终处于三种操作状态之一：空闲状态，表漫游状态或数据传输状态。DMA序列通过这三个取决于DMA控制寄存器的内容由微处理器初始化。空闲状态
DMAC在空闲状态下从复位开始。它处于空闲状态状态，直到DMAC启用（DMAEN设置为1）。它返回到DMAC完成请求的操作时的空闲状态（正常或有错误）。直到所有错误状态位被清除，DMAEN再次设置为1。数据传输状态当设置DMAEN时，DMAC直接进入数据传输状态，除非设置了桌面漫游（TW）位。如果设置了TW，则DMAC表在进入数据传输状态之前进行遍历。在任何一种情况下，当进入数据传输状态时，DMAC在本地DRAM和WD33C93（SCSI总线）之间移动数据接口控制器）。DMAC在本地DRAM中读取/写入数据
DMAC Initiation Mode
The DMAC has two initiation modes: direct and command
chaining (scatter-gather).
In the direct mode, the data address pointer and the byte count are
loaded into the chip.
In the command chaining mode, a table of data addresses and byte
counts is placed in local RAM and the address of the table is loaded
into the chip. The chip walks through the addresses and byte counts
from the local RAM to move each block of data as indicated by the
table. Scatter-gather operations are supported by command
chaining.
The PCC can DMA to/from local DRAM and VMEbus memory
only. Any other access results in a local bus time-out.
DMAC Operation States
The DMAC is always in one of three operational states: idle state,
table walk state, or data transfer state. The DMA sequences through
the three depending upon the contents of the DMA control register
which is initialized by the MPU.
Idle State
The DMAC starts out from reset in the idle state. It stays in the idle
state until the DMAC is enabled (DMAEN set to 1). It returns to the
idle state when the DMAC has completed the requested operations
(normally or with error). It does not leave the idle state again until
all error status bits are cleared and DMAEN is again set to 1.
Data Transfer State
When DMAEN is set, the DMAC goes directly to the data transfer
state unless the Table Walk (TW) bit is set. If TW is set, the DMAC
table walks before entering the data transfer state.
In either event, when the data transfer state is entered, the DMAC
moves data between local DRAM and the WD33C93 (SCSI bus
interface controller). The DMAC reads/writes data in local DRAM
