1336F-BRF50-AA-EN-HAS2半导体模块，A-B使用数据
使用数据地址寄存器中包含的地址。数据传输继续，直到字节计数寄存器达到0。此时，DMAC设置完成位并进入空闲状态除非字节中的链接位指示更多的表遍历计数寄存器。
桌子行走状态表地址和表功能代码寄存器指向DMAC表。表5-1是一个示例。该表有两个条目每个数据块：数据地址和字节数。当DMAC表移动时，它从表放入表地址寄存器，第二个长字从将表放入字节计数寄存器。
1336F-BRF50-AA-EN-HAS2半导体模块然后转到数据传输状态如果表遍历导致设置链接位，则DMAC表数据传输状态结束后再次行走。注意：DMAC表必须始终放置在32位内记忆力如果是8位或16位内存，则PCC终止在桌子行走过程中遇到。SCSI数据总线转换器WD33C93连接到PCC上的单独8位数据总线，并不是本地MC68030总线。这允许PCC收集一个通过从WD33C93，不使用处理器总线。当一个长单词是准备就绪后，芯片请求本地总线并传输。本方案减轻MC68030本地总线上的负载。SCSI芯片接口PCC为MC68030访问WD33C93。它使用非多路模式，这需要软件使用WD33C93指针寄存器访问其内部寄存器。WD33C93寄存器可以间接访问通过FFFE4000美元的地址寄存器。可编程滴答定时器PCC具有两个16位可编程滴答定时器。计时器以编程的方式向MC68030生成周期性中断速度周期为6.25µs至0.4秒，增量为6.25µs。这个计时器也可能被禁用。计时器中断级别为可编程，当其中断已确认。
using the address contained in the data address register. Data
transfers continue until the byte count register reaches 0.
At this point, the DMAC sets the done bit and enters the idle state
unless more table walking is indicated by the link bit in the byte
count register.
Table Walk State
The table address and table function code registers point to the
DMAC table. Table 5-1 is an example. The table has two entries for
each data block: the data address and the byte count.
When the DMAC table walks, it copies the first longword from the
table into the table address register, and the second longword from
the table into the byte count register. It then goes to the data transfer
state. If the table walk caused the link bit to be set, the DMAC table
walks again after the data transfer state has ended.
Note The DMAC table must always be placed within 32-bit
memory. The PCC terminates if 8-bit or 16-bit memory
is encountered during a table walk.SCSI Data Bus Converter
The WD33C93 connects to a separate 8-bit data bus on the PCC and
not to the local MC68030 bus. This allows the PCC to collect one
longword of data by transferring one byte at a time from the
WD33C93 without using the processor bus. When a longword is
ready, the chip requests the local bus and transfers it. This scheme
lightens the load on the MC68030 local bus.
SCSI Chip Interface
The PCC provides the interface for MC68030 accesses of the
WD33C93. It uses the nonmultiplexed mode which requires that
the software use the WD33C93 pointer registers to access its
internal registers. The WD33C93 registers are accessible indirectly
through the address register at $FFFE4000.
Programmable Tick Timers
The PCC features two 16-bit programmable tick timers. A timer
generates a periodic interrupt to the MC68030 at the programmed
rate. The period is 6.25 µs to 0.4 seconds in 6.25 µs increments. The
timer may also be disabled. The timer interrupt level is
programmable and it provides a status/ID vector when its
interrupt is acknowledged.
