3BHE028761R0101使用教程，ABB卡件
通道定序器和雙端口寄存器控制當(dāng)VMIVME-3112在任何掃描模式下運行時，操作由車載通道定序器控制。例如當(dāng)電路板通電時，轉(zhuǎn)換序列從通道00開始如第3.5.1節(jié)所述。A/D轉(zhuǎn)換完成后，雙端口控制邏輯接收轉(zhuǎn)換后的數(shù)據(jù)并將其存儲在該通道的適當(dāng)?shù)碾p端口寄存器。通道計數(shù)器增加1，選擇下一個多路復(fù)用到ADC的通道。
3BHE028761R0101使用教程同時選擇下一個通道，啟動新的a/D轉(zhuǎn)換序列。什么時候所有輸入通道均已轉(zhuǎn)換和存儲，通道計數(shù)器已重置至“零”，并再次啟動通道掃描序列（自動掃描僅模式）可編程間隔計時器三重16位計時器（可級聯(lián)至48位）可編程為觸發(fā)ADC掃描序列的開始。例如，可能需要每秒只更新一次數(shù)字化數(shù)據(jù)。董事會可以設(shè)置為掃描中斷模式。計時器將被設(shè)置為生成每秒脈沖一次。該脈沖將啟動ADC掃描序列。
一旦所有通道數(shù)字化并存儲，掃描結(jié)束中斷將生成到CPU以指示數(shù)據(jù)可用。中斷服務(wù)例程將數(shù)據(jù)讀入內(nèi)存，然后重新初始化總線下一個中斷的中斷器模塊（BIM）。
3.10總線斷路器模塊（BIM）MC68153 BIM處理與VMEbus的所有中斷接口。一中斷可以在任何VMEbus級別（1到7）上生成。取決于在所使用的模式下，可以在完成單個A/D轉(zhuǎn)換，或在完成16到64通道掃描時。BIM在生成一個中斷請求，并響應(yīng)來自CPU板。在680X0 CPU中，該8位向量乘以4計算出的地址加上VBR（矢量基址寄存器）指向該位置用于讀取ADC數(shù)字化數(shù)據(jù)的中斷服務(wù)例程。中斷程序示例見第4節(jié)。如果VMIVME-3112和背板上可能需要CPU和IACK跳線
CHANNEL SEQUENCER AND DUAL PORT REGISTER CONTROL
When the VMIVME-3112 is operated in any of the scanning modes,
the operation is controlled by an on-board channel sequencer. For example,
when the board is powered-on, a conversion sequence begins at Channel 00
as discussed in Section 3.5.1. Once the A/D conversion is completed, the dual
port control logic takes the converted data and stores it in that channel's
appropriate dual port register. The channel counter is incremented by one,
which selects the next channel to be multiplexed to the ADC. Concurrently with
selecting the next channel, a new A/D conversion sequence is initiated. When
all input channels have been converted and stored, the channel counter is reset
to "zero" and starts the channel scanning sequence again (AUTO SCANNING
MODE only)PROGRAMMABLE INTERVAL TIMER
A triple, 16-bit timer (cascadeable to 48 bits) may be programmed to
trigger the start of an ADC scan sequence. For example, it might be required to
get updated digitized data only once every second. The board could be set for
the SCANNING INTERRUPT MODE. The timer would be set to generate a
pulse once every second. That pulse would initiate the ADC scan sequence.
Once all channels are digitized and stored, an end of scan interrupt would be
generated to the CPU to indicate that data is available. The interrupt service
routine would read the data into memory and then re-initialize the Bus
Interrupter Module (BIM) for the next interrupt.
3.10 BUS INTERRUPTER MODULE (BIM)
An MC68153 BIM handles all interrupt interfacing to the VMEbus. An
interrupt may be generated on any VMEbus level (1 through 7). Depending on
the mode used, an interrupt may be generated upon the completion of a single
A/D conversion, or upon the completion of a 16- through 64-channel scan.
The BIM generates an 8-bit vector (D08(O)) after generating an
Interrupt Request and in response to the Interrupt Acknowledge cycle from the
CPU board. This 8-bit vector is multiplied by four in the 680X0 CPU and this
calculated address plus the VBR (Vector Base Register) points to the location
of the interrupt service routine to read the ADC digitized data. An interrupt
program example is found in Section 4. If there are empty backplane slots between the VMIVME-3112 and
the CPU, then IACK jumpers may be needed on the backplane
