PDD205A1121 3BHE025335R1121控制器模块，ABB使用配置手册
虽然从地址修改器寄存器中的所有位可以动态更改，但必须更改仅当VMEchip控制VMEbus时。更换从机的建议步骤地址修饰符为：a、 在请求程序配置中设置DWB位注册到1。
b、 读取DHB状态位，直到其为1。c、 更改从地址修改器寄存器。d、 将DWB位清除为0。寄存器允许软件对地址进行编程由MVME147驱动的修改器代码VMEbus循环。这五个位与AMSEL结合，允许软件动态选择主机访问的地址空间在VMEbus循环期间。
PDD205A1121 3BHE025335R1121控制器模块将这五位中的任何一位设置为1都会导致驱动相应地址修饰符行的主机高（如果AMSEL位设置为1）。将任何位清除为0会导致主机驱动对应线路为低电平（如果AMSEL位设置为1）。这些位由SYSRESET清除。位7软件使用AMSEL控制位定义VMEbus期间由主机驱动的AM代码源周期将位设置为1会导致主机驱动将六位降到地址修饰符行上。没有尝试用于检查存储在此寄存器中的值是否保留或非法的地址修饰符。清除AMSEL位使主机确定AM动态编码。AMSEL通常应清除为0。该位被清除系统重置。该寄存器用于使MC68030能够响特定VMEbus中断请求。请注意PCC中的主中断启用位也必须设置让VMEbus IRQ连接到MC68030。设置第1位到第7位中的任何一位都会取消屏蔽中断来自VMEbus IRQ信号的请求相应级别。请记住，只有一个VMEbus主机可以处理VMEbus IRQ。软件应设置这些位照着这些位通过任何重置被清除。
Although all bits in the slave address modifier register
may be changed dynamically, they must be changed
only when the VMEchip has control of the VMEbus.
The recommended procedure for changing the slave
address modifier is:
a. Set the DWB bit in the requester configuration
register to 1.
b. Read the DHB status bit until it is 1.
c. Change the slave address modifier register.
d. Clear the DWB bit to 0. The register allows software to program the address
modifier code that is driven by the MVME147 during a
VMEbus cycle. These five bits, in conjunction with AMSEL, allow software to
select dynamically the address space that the master accesses
during VMEbus cycles. Setting any of these five bits to 1 causes
the master to drive the corresponding address modifier line to
high (if the AMSEL bit is set to 1).
Clearing any of the bits to 0 causes the master to drive the
corresponding line to low (if the AMSEL bit is set to 1).
These bits are cleared by SYSRESET.
Bit 7 Software uses the AMSEL control bit to define what is the
source of the AM code driven by the master during a VMEbus
cycle.
Setting the bit to 1 causes the master to drive the contents of the
lower six bits onto the address modifier lines. No attempt is
made to check the value stored in this register for reserved or
illegal address modifiers.
Clearing the AMSEL bit causes the master to determine the AM
code dynamically.
AMSEL should normally be cleared to 0. This bit is cleared by
SYSRESET. This register is used to enable the MC68030 to respond
to specific VMEbus interrupt requests. Note that the
master interrupt enable bit in the PCC must also be set
for VMEbus IRQs to get through to the MC68030.
Setting any of bits 1 through 7 unmasks an interrupt
request from the VMEbus IRQ signal at the
corresponding level. Keep in mind that only one
VMEbus master is allowed to handle each level of
VMEbus IRQ. The software should set these bits
accordingly. These bits are cleared by any reset.
