參數(shù)資料
型號(hào)： 101-0654
廠商： Rabbit Semiconductor
文件頁(yè)數(shù)： 74/110頁(yè)
文件大?。?/td> 0K
描述： INTERFACE OP6800 W/ETHERNET 512K
標(biāo)準(zhǔn)包裝： 10
系列： SBC
模塊/板類(lèi)型： 單板計(jì)算機(jī)模塊
適用于相關(guān)產(chǎn)品： OP6800
62
MiniCom (OP6800)
B.3 Chip Select Circuit
Figure B-1 shows a schematic of the chip select circuit located on the OP6800 module.
Figure B-1. Chip Select Circuit
The current drain on the battery in a battery-backed circuit must be kept at a minimum.
When the OP6800 is not powered, the battery keeps the SRAM memory contents and the
real-time clock (RTC) going. The SRAM has a powerdown mode that greatly reduces
power consumption. This powerdown mode is activated by raising the chip select (CS)
signal line. Normally the SRAM requires Vcc to operate. However, only 2 V is required
for data retention in powerdown mode. Thus, when power is removed from the circuit, the
battery voltage needs to be provided to both the SRAM power pin and to the CS signal
line. The CS control circuit accomplishes this task for the SRAM’s chip select signal line.
In a powered-up condition, the CS control circuit must allow the processor’s chip select
signal /CS1 to control the SRAM’s CS signal /CSRAM. So, with power applied, /CSRAM
must be the same signal as /CS1, and with power removed, /CSRAM must be held high
(but only needs to be battery voltage high). Q3 and Q4 are MOSFET transistors with com-
plementary polarity. They are both turned on when power is applied to the circuit. They
allow the CS signal to pass from the processor to the SRAM so that the processor can peri-
odically access the SRAM. When power is removed from the circuit, the transistors will
turn off and isolate /CSRAM from the processor. The isolated /CSRAM line has a 100 k
pullup resistor to VRAM (R28). This pullup resistor keeps /CSRAM at the VRAM voltage
level (which under no power condition is the backup battery’s regulated voltage at a little
more than 2 V).
Transistors Q3 and Q4 are of opposite polarity so that a rail-to-rail voltage can be passed.
When the /CS1 voltage is low, Q3 will conduct. When the /CS1 voltage is high, Q4 con-
ducts. It takes time for the transistors to turn on, creating a propagation delay. This propa-
gation delay is typically very small, about 10 ns to 15 ns.
/CS1
/CSRAM
/RESET_OUT
Q3
Q4
R28
VRAM
100 kW
VRAM
SWITCH
相關(guān)PDF資料
PDF描述
046232108015800 CONN FFC/FPC 8POS 1MM VERT SMD
395-030-520-201 CARD EDGE 30POS DL .100X.200 BLK
20-101-0463 COMPUTER SINGLE-BOARD BL2120
20-101-1220 COMPUTER SINGLE-BOARD BL4S200
006200512230000+ CONN FFC/FPC 12POS 1MM R/A SMD
相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
101-0655 功能描述:開(kāi)發(fā)軟件 SNMP Module CD RoHS:否 制造商:Atollic Inc. 產(chǎn)品:Compilers/Debuggers 用于:ARM7, ARM9, Cortex-A, Cortex-M, Cortex-R Processors
10106551-JCB64LF 功能描述:板對(duì)板與夾層連接器 TRX EXT H-7ZCND0982 JRC RoHS:否 制造商:JAE Electronics 系列:WP3 產(chǎn)品類(lèi)型:Receptacles 節(jié)距:0.4 mm 疊放高度:1 mm 安裝角: 位置/觸點(diǎn)數(shù)量:50 排數(shù):2 外殼材料:Plastic 觸點(diǎn)材料:Copper Alloy 觸點(diǎn)電鍍:Gold 電壓額定值:50 V 電流額定值:0.4 A
10106552-NFB71LF 功能描述:板對(duì)板與夾層連接器 NFB71LF10106552F.NEC RoHS:否 制造商:JAE Electronics 系列:WP3 產(chǎn)品類(lèi)型:Receptacles 節(jié)距:0.4 mm 疊放高度:1 mm 安裝角: 位置/觸點(diǎn)數(shù)量:50 排數(shù):2 外殼材料:Plastic 觸點(diǎn)材料:Copper Alloy 觸點(diǎn)電鍍:Gold 電壓額定值:50 V 電流額定值:0.4 A
10106555-002LF 制造商:FCI 功能描述:511-526F-USB 制造商:FCI 功能描述:OEM ITEM 511-526F-USB
101-0656 功能描述:開(kāi)發(fā)軟件 PPP Module CD RoHS:否 制造商:Atollic Inc. 產(chǎn)品:Compilers/Debuggers 用于:ARM7, ARM9, Cortex-A, Cortex-M, Cortex-R Processors
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