BENTLY 330180-90-05通道溫度模塊
裝運的EPROM通常用于車載調(diào)試器固件（177Bug），但可用于下載用戶代碼閃爍。EPROM只占1MB內(nèi)存，但可以使用前2MB閃存共享前2MB空間。這個在混合模式下，EPROM僅占用ROM空間中的1MB空間并將在第二個1MB空間中重復（為未來擴展）。EPROM可以與2MB的Flash，或者可以用來編程所有4MB的Flash，然后是J8可以移除跳線，以僅使用閃光燈。
BENTLY 330180-90-05通道溫度模塊系統(tǒng)重置后，EPROM映射到默認值地址為$00000到$FFFFF，可以映射到如果需要，從$FF800000到$FF8FFFFF。之間的控制映射EPROM/閃存混合模式和所有閃存模式由外部板跳線J8和VMEchip2位的組合GPIO2。表4-1顯示了“閃存”跳線和GPIO位2的方式更改EPROM/閃存配置SRAM允許調(diào)試器操作并限制診斷在沒有DRAM夾層的情況下執(zhí)行。SRAM不會支持突發(fā)循環(huán)。SRAM由VMEchip2控制，訪問時間可編程。請參閱中的VMEchip2有關(guān)更多詳細信息，請參閱單板計算機程序員參考指南。這些板上安裝了100個ns SRAM。MVME177上可選提供SRAM備用電池。這個電池備份功能由Dallas DS1210S提供。只有一個MVME177支持備用電源。電池當主電源斷開時，向SRAM提供VCC。每次MVME177通電時，DS1210都會檢查電源。如果備用電源的電壓低于2伏，第二個存儲周期被阻塞。這允許軟件提供早期警告，以避免數(shù)據(jù)丟失。因為DS1210可能會阻塞第二次訪問，軟件應至少做兩次在依賴數(shù)據(jù)之前訪問。MVME177可選提供跳線，允許電源連接到VMEbus+5 V STDBY引腳的DS1210源或車載電池。SRAM的可選電源為插座式三洋CR2430電池。提供一個小電容器以允許電池在不丟失數(shù)據(jù)的情況下快速更換。電池的壽命在很大程度上取決于環(huán)境電路板溫度和通電占空比。FB1225CR2430鋰電池應提供至少兩年的電路板斷電且電路板溫度為40°C時的備份時間。如果通電占空比為50%（電路板通電一半電池壽命為四年。在較低的環(huán)境溫度下溫度備份時間大大延長，可能接近電池的保質(zhì)期。
The EPROMs as shipped are normally used for the onboard
debugger firmware (177Bug), but could be used to download user
code to Flash. The EPROMs make up only 1MB of memory, but can
share the first 2MB of space with the first 2MB of Flash. The
EPROMs occupy only 1MB space in the ROM space in mixed mode
and will be repeated in the second 1MB space (which is reserved for
future expansion). The EPROMs could coexist with this 2MB of
Flash, or could be used to program all 4MB of Flash, then the J8
jumper could be removed to make only Flash available.
After a system reset, the EPROMs are mapped to the default
addresses $00000 through $FFFFF, and could be mapped to
$FF800000 through $FF8FFFFF if needed. The control between
mapping EPROM/Flash mixed mode and all Flash mode is done by
the combination of external board jumper J8 and the VMEchip2 bit
GPIO2. Table 4-1 shows how the “Flash” jumper and GPIO bit 2
change the EPROM/Flash configurationThe SRAM allows the debugger to operate and limited diagnostics
to be executed without the DRAM mezzanine. The SRAM will not
support burst cycles. The SRAM is controlled by the VMEchip2,
and the access time is programmable. Refer to the VMEchip2 in the
Single Board Computers Programmer's Reference Guide for more detail.
The boards are populated with 100 ns SRAMs.
SRAM battery backup is optionally available on the MVME177. The
battery backup function is provided by a Dallas DS1210S. Only one
backup power source is supported on the MVME177. The battery
supplies VCC to the SRAMs when main power is removed.
Each time the MVME177 is powered up, the DS1210S checks the
power source. If the voltage of the backup source is less than two
volts, the second memory cycle is blocked. This allows software to provide an early warning to avoid data loss. Because the DS1210S
may block the second access, the software should do at least two
accesses before relying on the data.
Optionally, the MVME177 provides jumpers that allow the power
source of the DS1210S to connect to the VMEbus +5 V STDBY pin
or the onboard battery.
The optional power source for the SRAM is a socketed Sanyo
CR2430 battery. A small capacitor is provided to allow the battery
to be quickly replaced without data loss.
The lifetime of the battery is very dependent on the ambient
temperature of the board and the power-on duty cycle. The FB1225
and CR2430 lithium batteries should provide at least two years of
backup time with the board powered off and the board at 40? C. If
the power-on duty cycle is 50% (the board is powered on half of the
time), the battery lifetime is four years. At lower ambient
temperatures the backup time is greatly extended and may
approach the shelf life of the battery.
