UFC911B106 3BHE037864R0106控制處理器,ABB中文說明
VMEbus系統(tǒng)控制器VMEchip提供的眾多功能之一是VMEbus系統(tǒng)控制器功能。系統(tǒng)控制器包括以下內(nèi)容：? VMEbus全局超時(shí)計(jì)時(shí)器? 系統(tǒng)時(shí)鐘（SYSCLK*）驅(qū)動(dòng)程序? 仲裁人? 中斷確認(rèn)（IACK*）菊花鏈驅(qū)動(dòng)程序。此處還描述了系統(tǒng)重置實(shí)用程序，因?yàn)樗褑⒂卯?dāng)MVME147為系統(tǒng)控制器時(shí)。系統(tǒng)控制器功能由標(biāo)題J3啟用/禁用。
UFC911B106 3BHE037864R0106控制處理器當(dāng)MVME147系統(tǒng)控制器，系統(tǒng)控制器（SCON）LED亮起。VMEbus超時(shí)當(dāng)數(shù)據(jù)選通（DS0*或DS1*）處于活動(dòng)狀態(tài)，當(dāng)兩者都處于非活動(dòng)狀態(tài)時(shí)，將被禁用。如果在數(shù)據(jù)選通停止前計(jì)時(shí)器超時(shí)，總線錯(cuò)誤（BERR*）信號(hào)被激活。超時(shí)時(shí)間由計(jì)時(shí)器間隔寄存器，可以是102μs、205μs、410μs或無限。系統(tǒng)時(shí)鐘實(shí)用程序
16 MHz系統(tǒng)時(shí)鐘被驅(qū)動(dòng)到VMEbus SYSCLK上*VMEchip系統(tǒng)時(shí)鐘驅(qū)動(dòng)器的信號(hào)線。
VMEchip實(shí)現(xiàn)了兩種不同的仲裁模式。他們優(yōu)先順序和循環(huán)。該模式可由軟件選擇。在優(yōu)先模式下，仲裁器優(yōu)先處理總線請(qǐng)求向最高優(yōu)先級(jí)的請(qǐng)求者發(fā)出信號(hào)并做出響應(yīng)。仲裁器還通過激活當(dāng)來自更高優(yōu)先級(jí)的請(qǐng)求時(shí)，總線清除（BCLR*）信號(hào)主節(jié)點(diǎn)已在循環(huán)模式下接收，仲裁人在循環(huán)模式下分配總線優(yōu)先權(quán)基礎(chǔ)。循環(huán)賽中不使用BCLR*信號(hào)模式仲裁器還包含超時(shí)功能。它激活總線繁忙（BBSY*），如果請(qǐng)求者未在超時(shí)期。超時(shí)時(shí)間段可由軟件選擇，并且可以設(shè)置為410μs或無窮大。IACK*菊花鏈驅(qū)動(dòng)器IACK*菊花鏈驅(qū)動(dòng)器激活中斷確認(rèn)
每當(dāng)中斷處理程序確認(rèn)中斷請(qǐng)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.
