SB822邏輯模塊,ABB產(chǎn)品外觀
P2信號多路復用由于P2背板連接器中可用引腳的供應有限在為MVME761輸入/輸出模式配置的MVME2700機型中，某些信號通過VMEbus連接器P2多路傳輸，用于額外的輸入/輸出容量。
受影響的信號是在之間傳遞的同步輸入/輸出控制信號基板和MVME761過渡模塊。多路復用是對軟件完全透明的硬件功能。
SB822邏輯模塊P2多路復用功能涉及四個信號：MXDO、MXDI、，MXCLK和MXSYNC?.MXDO是來自主板和MXDI是來自MVME761模塊的時間多路復用線路。MXCLK公司是用于MXDO和MXDI數(shù)據(jù)線的10 MHz位時鐘。MXSYNC? 是在時隙15（參考下表）由MVME2700基板。MVME761轉(zhuǎn)換模塊使用MXSYNC? 與基本boardABORT開關(guān)（S1）同步中止開關(guān)位于LED夾層上。它可以由軟件以及手工操作。當通過軟件啟用時，中止開關(guān)可以向處理器生成中斷信號。中斷正常用于中止程序執(zhí)行并將控制返回給調(diào)試器固件位于MVME2700 EPROM和閃存中。這個中斷信號通過ISA總線中斷線到達處理器模塊IRQ8?. 該信號也可在Z8536 CIO設(shè)備的引腳PB7處獲得，它處理各種狀態(tài)信號、串行輸入/輸出線和計數(shù)器。連接到中止開關(guān)的斷路器是一個邊緣敏感電路，過濾以消除開關(guān)反彈。
復位開關(guān)（S2）復位開關(guān)位于LED夾層上。復位開關(guān)重置所有車載設(shè)備；它還驅(qū)動系統(tǒng)重置? 如果MVME2700是系統(tǒng)控制器。Universe II ASIC包括全局和局部復位驅(qū)動器。什么時候Universe II作為VMEbus系統(tǒng)控制器、復位驅(qū)動器運行通過斷言VMEbus信號SYSRESET來提供全局系統(tǒng)重置?.系統(tǒng)重置? 信號可能由復位開關(guān)產(chǎn)生，通電重置、看門狗超時或通過雜項控件中的控制位在Universe II ASIC中注冊（MISC_CTL）。系統(tǒng)重置? 殘余根據(jù)VMEbus規(guī)范的要求，至少斷言200毫秒。類似地，Universe II ASIC提供輸入信號和控制位啟動本地重置操作。通過設(shè)置控制位，軟件可以將電路板保持在重置狀態(tài)，禁止故障電路板參與在正常系統(tǒng)操作中。即使在以下情況下，也會啟用本地重置驅(qū)動程序Universe II ASIC不是系統(tǒng)控制器。本地重置可能是由重置開關(guān)、通電重置、看門狗超時、VMEbus系統(tǒng)重置?, 或MISC\U CTL寄存器中的控制位。
P2 Signal Multiplexing
Due to the limited supply of available pins in the P2 backplane connectors
of MVME2700 models that are configured for MVME761 I/O mode,
certain signals are multiplexed through VMEbus connector P2 for
additional I/O capacity.
The signals affected are synchronous I/O control signals that pass between
the base board and the MVME761 transition module. The multiplexing is
a hardware function that is entirely transparent to software.
Four signals are involved in the P2 multiplexing function: MXDO, MXDI,
MXCLK, and MXSYNC?.
MXDO is a time-multiplexed data output line from the main board and
MXDI is a time-multiplexed line from the MVME761 module. MXCLK
is a 10 MHz bit clock for the MXDO and MXDI data lines. MXSYNC? is
asserted for one bit time at time slot 15 (refer to the following table) by the
MVME2700 base board. The MVME761 transition module uses
MXSYNC? to synchronize with the base boardABORT Switch (S1)
The ABORT switch is located on the LED mezzanine. It can be actuated by
software as well as by hand. When enabled by software, the ABORT switch
can generate an interrupt signal to the processor. The interrupt is normally
used to abort program execution and return control to the debugger
firmware located in the MVME2700 EPROM and Flash memory. The
interrupt signal reaches the processor module via ISA bus interrupt line
IRQ8?. The signal is also available at pin PB7 of the Z8536 CIO device,
which handles various status signals, serial I/O lines, and counters.The interrupter connected to the ABORT switch is an edge-sensitive circuit,
filtered to remove switch bounce.
RESET Switch (S2)
The RESET switch is located on the LED mezzanine. The RESET switch
resets all onboard devices; it also drives a SYSRESET? signal if the
MVME2700 is the system controller.
The Universe II ASIC includes both a global and a local reset driver. When
the Universe II operates as the VMEbus system controller, the reset driver
provides a global system reset by asserting the VMEbus signal SYSRESET?.
A SYSRESET? signal may be generated by the RESET switch, a power-up
reset, a watchdog timeout, or by a control bit in the Miscellaneous Control
Register (MISC_CTL) in the Universe II ASIC. SYSRESET? remains
asserted for at least 200 ms, as required by the VMEbus specification.
Similarly, the Universe II ASIC supplies an input signal and a control bit
to initiate a local reset operation. By setting a control bit, software can
maintain a board in a reset state, disabling a faulty board from participating
in normal system operation. The local reset driver is enabled even when
the Universe II ASIC is not system controller. Local resets may be
generated by the RESET switch, a power-up reset, a watchdog timeout, a
VMEbus SYSRESET?, or a control bit in the MISC_CTL register.
