参数资料
| 型号： | XR16M2651IM48-F |
| 厂商： | Exar Corporation |
| 文件页数： | 3/51页 |
| 文件大小： | 0K |
| 描述： | IC UART FIFO 32B DUAL 48TQFP |
| 标准包装： | 250 |
| 特点： | * |
| 通道数： | 2，DUART |
| FIFO's： | 32 字节 |
| 规程： | RS232，RS422 |
| 电源电压： | 1.62 V ~ 3.63 V |
| 带自动流量控制功能： | 是 |
| 带IrDA 编码器/解码器： | 是 |
| 带故障启动位检测功能： | 是 |
| 带调制解调器控制功能： | 是 |
| 带CMOS： | 是 |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 48-TQFP |
| 供应商设备封装： | 48-TQFP（7x7） |
| 包装： | 托盘 |
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XR16M2651
11
REV. 1.0.2
HIGH PERFORMANCE DUART WITH 32-BYTE FIFO AND POWERSAVE FEATURE
2.7
Crystal Oscillator or External Clock Input
The M2651 includes an on-chip oscillator (XTAL1 and XTAL2) to produce a clock for both UART sections in the
device. The CPU data bus does not require this clock for bus operation. The crystal oscillator provides a
system clock to the Baud Rate Generators (BRG) section found in each of the UART. XTAL1 is the input to the
oscillator or external clock buffer input with XTAL2 pin being the output. For programming details, see
FIGURE 4. TYPICAL CRYSTAL CONNECTIONS
The on-chip oscillator is designed to use an industry standard microprocessor crystal (parallel resonant,
fundamental frequency with 10-22 pF capacitance load, ESR of 20-120 ohms and 100 ppm frequency
tolerance) connected externally between the XTAL1 and XTAL2 pins (see Figure 4). The programmable Baud
Rate Generator is capable of operating with a crystal oscillator frequency of up to 24 MHz. However, with an
external clock input on XTAL1 pin, it can extend its operation up to 64 MHz (16 Mbps serial data rate) at 3.3V
with an 4X sampling rate. For further reading on the oscillator circuit please see the Application Note DAN108
on the EXAR web site at http://www.exar.com.
2.8
Programmable Baud Rate Generator with Fractional Divisor
Each UART has its own Baud Rate Generator (BRG) with a prescaler for the transmitter and receiver. The
prescaler is controlled by a software bit in the MCR register. The MCR register bit-7 sets the prescaler to divide
the input crystal or external clock by 1 or 4. The output of the prescaler clocks to the BRG. The BRG further
divides this clock by a programmable divisor between 1 and (216 - 0.0625) in increments of 0.0625 (1/16) to
obtain a 16X or 8X or 4X sampling clock of the serial data rate. The sampling clock is used by the transmitter
for data bit shifting and receiver for data sampling. The BRG divisor (DLL, DLM and DLD registers) defaults to
the value of ’1’ (DLL = 0x01, DLM = 0x00 and DLD = 0x00) upon reset. Therefore, the BRG must be
programmed during initialization to the operating data rate. The DLL and DLM registers provide the integer part
of the divisor and the DLD register provides the fractional part of the dvisior. Only the four lower bits of the DLD
are implemented and they are used to select a value from 0 (for setting 0000) to 0.9375 or 15/16 (for setting
1111). Programming the Baud Rate Generator Registers DLL, DLM and DLD provides the capability for
selecting the operating data rate. Table 6 shows the standard data rates available with a 24MHz crystal or
external clock at 16X clock rate. If the pre-scaler is used (MCR bit-7 = 1), the output data rate will be 4 times
less than that shown in Table 6. At 8X sampling rate, these data rates would double and at 4X sampling rate,
they would quadruple. Also, when using 8X or 4X sampling mode, please note that the bit-time will have a jitter
C1
22-47pF
C2
22-47pF
Y1
1.8432 MHz
to
24 MHz
R1
0-120
(Optional)
R2
500K - 1M
XTAL1
XTAL2
相关PDF资料 |
PDF描述 |
|---|---|
| XR16M2750IM48-F | IC UART FIFO 64B DUAL 48TQFP |
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相关代理商/技术参数 |
参数描述 |
|---|---|
| XR16M2651IM48TR-F | 制造商:Exar Corporation 功能描述:UART 2-CH 32Byte FIFO 1.8V/2.5V/3.3V 48-Pin TQFP T/R 制造商:Exar Corporation 功能描述:XR16M2651IM48TR-F |
| XR16M2750 | 制造商:EXAR 制造商全称:EXAR 功能描述:HIGH PERFORMANCE DUART WITH 64-BYTE FIFO |
| XR16M2750IL-0A-EB | 功能描述:界面开发工具 Eval Board for XR16M2750IL-0A RoHS:否 制造商:Bourns 产品:Evaluation Boards 类型:RS-485 工具用于评估:ADM3485E 接口类型:RS-485 工作电源电压:3.3 V |
| XR16M2750IL-0B-EB | 功能描述:界面开发工具 Eval Board for XR16M2750IL Series RoHS:否 制造商:Bourns 产品:Evaluation Boards 类型:RS-485 工具用于评估:ADM3485E 接口类型:RS-485 工作电源电压:3.3 V |
| XR16M2750IL32 | 制造商:EXAR 制造商全称:EXAR 功能描述:HIGH PERFORMANCE DUART WITH 64-BYTE FIFO |
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