UFC911B106 3BHE037864R0106控制處理器,ABB中文說明
VMEbus系統控制器VMEchip提供的眾多功能之一是VMEbus系統控制器功能。系統控制器包括以下內容：? VMEbus全局超時計時器? 系統時鐘（SYSCLK*）驅動程序? 仲裁人? 中斷確認（IACK*）菊花鏈驅動程序。此處還描述了系統重置實用程序，因為它已啟用當MVME147為系統控制器時。系統控制器功能由標題J3啟用/禁用。
UFC911B106 3BHE037864R0106控制處理器當MVME147系統控制器，系統控制器（SCON）LED亮起。VMEbus超時當數據選通（DS0*或DS1*）處于活動狀態，當兩者都處于非活動狀態時，將被禁用。如果在數據選通停止前計時器超時，總線錯誤（BERR*）信號被激活。超時時間由計時器間隔寄存器，可以是102μs、205μs、410μs或無限。系統時鐘實用程序
16 MHz系統時鐘被驅動到VMEbus SYSCLK上*VMEchip系統時鐘驅動器的信號線。
VMEchip實現了兩種不同的仲裁模式。他們優先順序和循環。該模式可由軟件選擇。在優先模式下，仲裁器優先處理總線請求向最高優先級的請求者發出信號并做出響應。仲裁器還通過激活當來自更高優先級的請求時，總線清除（BCLR*）信號主節點已在循環模式下接收，仲裁人在循環模式下分配總線優先權基礎。循環賽中不使用BCLR*信號模式仲裁器還包含超時功能。它激活總線繁忙（BBSY*），如果請求者未在超時期。超時時間段可由軟件選擇，并且可以設置為410μs或無窮大。IACK*菊花鏈驅動器IACK*菊花鏈驅動器激活中斷確認
每當中斷處理程序確認中斷請求。
VMEbus System Controller
One of the many functions provided by the VMEchip is the
VMEbus system controller function. The system controller includes
the following:
? VMEbus global time-out timer
? System Clock (SYSCLK*) driver
? Arbiter
? Interrupt Acknowledge (IACK*) daisy-chain driver.
The system reset utility is also described here because it is enabled
when the MVME147 is system controller. The system controller
function is enabled/disabled by header J3. When the MVME147 is
system controller, the System Controller (SCON) LED is turned on.
VMEbus Time-Out
The VMEbus timer is started when either Data Strobe (DS0* or
DS1*) goes active and is disabled when they both go inactive. If the
timer times out before the data strobes go inactive, the Bus Error
(BERR*) signal is activated. The time-out period is controlled by the
timer interval register and may be 102 μs, 205 μs, 410 μs, or infinite.
System Clock Utility
The 16 MHz system clock is driven onto the VMEbus SYSCLK*
signal line by the VMEchip system clock driver.
Arbiter
The VMEchip implements two different arbitration modes. They
are prioritized and round-robin. The mode is software selectable.
In the prioritized mode, the arbiter prioritizes the bus request
signals and responds with grant to the highest priority requester.
The arbiter also informs the current bus master by activating the
Bus Clear (BCLR*) signal when a request from a higher priority
master has been receivedIn the round-robin mode, the arbiter assigns the bus on a rotating
priority basis. The BCLR* signal is not used in the round-robin
mode.
The arbiter also contains a time-out feature. It activates Bus Busy
(BBSY*) on its own if BBSY* is not activated by the requester within
the time-out period. The time-out period is software selectable and
may be set to 410 μs or infinite.
IACK* Daisy-Chain Driver
The IACK* daisy-chain driver activates the interrupt acknowledge
daisy-chain whenever an interrupt handler acknowledges an
interrupt request.
