ZHCSS40I march   1994  – march 2021 TL16C550C

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 说明
  4. 3 Revision History
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1  Absolute Maximum Ratings
    2. 5.2  Recommended Operating Conditions (Low Voltage - 3.3 nominal)
    3. 5.3  Recommended Operating Conditions (Standard Voltage - 5 V nominal)
    4. 5.4  Thermal Information
    5. 5.5  Electrical Characteristics (Low Voltage - 3.3 V nominal)
    6. 5.6  Electrical Characteristics (Standard Voltage - 5 V nominal)
    7. 5.7  System Timing Requirements
    8. 5.8  System Switching Characteristics
    9. 5.9  Baud Generator Switching Characteristics
    10. 5.10 Receiver Switching Characteristics
    11. 5.11 Transmitter Switching Characteristics
    12. 5.12 Modem Control Switching Characteristics
  7. 6 Parameter Measurement Information
  8. 7 Detailed Description
    1. 7.1 Autoflow Control (see )
    2. 7.2 Auto-RTS (see )
    3. 7.3 Auto-CTS (see )
    4. 7.4 Enabling Autoflow Control and Auto-CTS
    5. 7.5 Auto-CTS and Auto-RTS Functional Timing
    6. 7.6 Functional Block Diagram
    7. 7.7 Principles of Operation
      1. 7.7.1  Accessible Registers
      2. 7.7.2  FIFO Control Register (FCR)
      3. 7.7.3  FIFO Interrupt Mode Operation
      4. 7.7.4  FIFO Polled Mode Operation
      5. 7.7.5  Interrupt Enable Register (IER)
      6. 7.7.6  Interrupt Identification Register (IIR)
      7. 7.7.7  Line Control Register (LCR)
      8. 7.7.8  Line Status Register (LSR)
      9. 7.7.9  Modem Control Register (MCR)
      10. 7.7.10 Modem Status Register (MSR)
      11. 7.7.11 Programming Baud Generator
      12. 7.7.12 Receiver Buffet Register (RBR)
      13. 7.7.13 Scratch Register
      14. 7.7.14 Transmitter Holding Register (THR)
  9. 8 Application Information
  10. 9 Device and Documentation Support
    1. 9.1 接收文档更新通知
    2. 9.2 支持资源
    3. 9.3 Trademarks
    4. 9.4 静电放电警告
    5. 9.5 术语表
  11. 10Mechanical, Packaging, and Orderable Information

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7.7.11 Programming Baud Generator

The ACE contains a programmable baud generator that takes a clock input in the range between dc and 16 MHz and divides it by a divisor in the range between 1 and (216−1).The output frequency of the baud generator is sixteen times (16 x) the baud rate. The formula for the divisor is:

Equation 1. divisor = XIN frequency input ÷ (desired baud rate x 16)

Two 8-bit registers, called divisor latches, store the divisor in a 16-bit binary format. These divisor latches must be loaded during initialization of the ACE in order to ensure desired operation of the baud generator. When either of the divisor latches is loaded, a 16-bit baud counter is also loaded to prevent long counts on initial load.

Table 7-9 and Table 7-10 illustrate the use of the baud generator with crystal frequencies of 1.8432 MHz and 3.072 MHz respectively. For baud rates of 38.4 kbits/s and below, the error obtained is very small. The accuracy of the selected baud rate is dependent on the selected crystal frequency (refer to Figure 7-5 for examples of typical clock circuits).

Table 7-9 Baud Rates Using a 1.8432-MHz Crystal
DESIRED BAUD RATE DIVISOR USED TO GENERATE 16 x CLOCK PERCENT ERROR DIFFERENCE BETWEEN DESIRED AND ACTUAL
50 2304
75 1536
110 1047 0.026
134.5 857 0.058
150 768
300 384
600 192
1200 96
1800 64
2000 58 0.69
2400 48
3600 32
4800 24
7200 16
9600 12
19200 6
38400 3
56000 2 2.86
Table 7-10 Baud Rates Using a 3.072-MHz Crystal
DESIRED BAUD RATE DIVISOR USED TO GENERATE 16 x CLOCK PERCENT ERROR DIFFERENCE BETWEEN DESIRED AND ACTUAL
50 3840
75 2560
110 1745 0.026
134.5 1428 0.034
150 1280
300 640
600 320
1200 160
1800 107 0.312
2000 96
2400 80
3600 53 0.628
4800 40
7200 27 1.23
9600 20
19200 10
38400 5
GUID-20210201-CA0I-WKCK-QFN4-1WQG6V4BQNMF-low.png Figure 7-5 Typical Clock Circuits
Table 7-11 TYPICAL CRYSTAL OSCILLATOR NETWORK
CRYSTAL RP RX2 C1 C2
3.072 MHz 1 MW 1.5 kW 10 − 30 pF 40 − 60 pF
1.8432 MHz 1 MW 1.5 kW 10 − 30 pF 40 − 60 pF