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16C2850 参数 Datasheet PDF下载

16C2850图片预览
型号: 16C2850
PDF下载: 下载PDF文件 查看货源
内容描述: 双UART,具有128字节FIFO的和RS- 485半双工控制 [DUAL UART WITH 128-byte FIFO’s AND RS-485 HALF DUPLEX CONTROL]
分类和应用: 先进先出芯片
文件页数/大小: 44 页 / 670 K
品牌: EXAR [ EXAR CORPORATION ]
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XR16C2850  
DMA Operation  
(bits 0-1) control the modem -RI and -CD inputs  
respectively. MCR signals -DTR and -RTS (bits 0-1)  
are used to control the modem -CTS and -DSR inputs  
respectively. The transmitter output (TX) and the  
receiver input (RX) are disconnected from their asso-  
ciated interface pins, and instead are connected to-  
gether internally (see Figure 12). The -CTS, -DSR, -  
CD, and -RI are disconnected from their normal  
modemcontrolinputspins,andinsteadareconnected  
internally to -DTR, -RTS, -OP1 and -OP2. Loopback  
test data is entered into the transmit holding register  
via the user data bus interface, D0-D7. The transmit  
UART serializes the data and passes the serial data to  
the receive UART via the internal loopback connec-  
tion. The receive UART converts the serial data back  
into parallel data that is then made available at the  
user data interface, D0-D7. The user optionally com-  
pares the received data to the initial transmitted data  
for verifying error free operation of the UART TX/RX  
circuits.  
The 2850 FIFO trigger level provides additional flex-  
ibility to the user for block mode operation. LSR bits 5-  
6 provide an indication when the transmitter is empty  
or has an empty location(s). The user can optionally  
operate the transmit and receive FIFO in the DMA  
mode (FCR bit-3). When the transmit and receive  
FIFO are enabled and the DMA mode is deactivated  
(DMA Mode “0”), the 2850 activates the interrupt  
output pin for each data transmit or receive operation.  
When DMA mode is activated (DMA Mode “1”), the  
user takes the advantage of block mode operation by  
loading or unloading the FIFO in a block sequence  
determined by the preset trigger level. In this mode,  
the 2850 sets the interrupt output pin when characters  
in the transmit FIFO are below the transmit trigger  
level, or the characters in the receive FIFO are above  
the receive trigger level.  
Sleep Mode  
In this mode , the receiver and transmitter interrupts  
are fully operational. The Modem Control Interrupts  
are also operational. However, the interrupts can only  
be read using the lower four bits of the Modem Control  
Register (MCR bits 0-3) instead of the four Modem  
Status Register bits 4-7. The interrupts are still con-  
trolled by the IER.  
The 2850 is designed to operate with low power  
consumption. A special sleep mode is included to  
further reduce power consumption when the chip is  
not being used. With EFR bit-4 and IER bit-4 enabled  
(set to a logic 1), the 2850 enters the sleep mode but  
resumesnormaloperationwhenastartbitisdetected,  
a change of state on any of the modem input pins RX,  
-RI, -CTS, -DSR, -CD, or transmit data is provided by  
the user. If the sleep mode is enabled and the 2850 is  
awakened by one of the conditions described above,  
it will return to the sleep mode automatically after the  
last character is transmitted or read by the user. In any  
case, the sleep mode will not be entered while an  
interrupt(s) is pending. The 2850 will stay in the sleep  
mode of operation until it is disabled by setting IER bit-  
4 to a logic 0.  
Loopback Mode  
The internal loopback capability allows onboard diag-  
nostics. In the loopback mode the normal modem  
interface pins are disconnected and reconfigured for  
loopbackinternally. InthismodeMSRbits4-7arealso  
disconnected. However, MCR register bits 0-3 can be  
used for controlling loopback diagnostic testing. In the  
loopback mode, OP1 and OP2 in the MCR register  
Rev. 1.00P  
14  
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