SLLS177I March   1994  – March 2021 TL16C550C

PRODUCTION DATA  

  1. 1 Features
  2. 2 Description
  3. 3 Revision History
  4. 4 Pin Configuration and Functions
  5. 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
  6. 6 Parameter Measurement Information
  7. 7 Detailed Description
    1. 7.1 Autoflow Control (see Figure 1-1)
    2. 7.2 Auto-RTS (see Figure 1-1)
    3. 7.3 Auto-CTS (see Figure 1-1)
    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)
  8. 8 Application Information
  9. 9 Device and Documentation Support
    1. 9.1 Receiving Notification of Documentation Updates
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  10. 10Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.7.10 Modem Status Register (MSR)

The MSR is an 8-bit register that provides information about the current state of the control lines from the modem, data set, or peripheral device to the CPU. Additionally, four bits of this register provide change information; when a control input from the modem changes state, the appropriate bit is set. All four bits are cleared when the CPU reads the MSR. The contents of this register are summarized in Table 7-3 and are described in the following bulleted list.

  • Bit 0: This bit is the change in clear-to-send (ΔCTS) indicator. ΔCTS indicates that the CTS input has changed state since the last time it was read by the CPU. When ΔCTS is set (autoflow control is not enabled and the modem status interrupt is enabled), a modem status interrupt is generated. When autoflow control is enabled (ΔCTS is cleared), no interrupt is generated.
  • Bit 1: This bit is the change in data set ready (ΔDSR) indicator. ΔDSR indicates that the DSR input has changed state since the last time it was read by the CPU. When ΔDSR isset and the modem status interrupt is enabled, a modem status interrupt is generated.
  • Bit 2: This bit is the trailing edge of the ring indicator (TERI) detector. TERI indicates that the RI input to the chip has changed from a low to a high level. When TERI is set and the modem status interrupt is enabled, a modem status interrupt is generated.
  • Bit 3: This bit is the change in data carrier detect (ΔDCD) indicator. ΔDCD indicates that the DCD input to the chip has changed state since the last time it was read by the CPU. When ΔDCD is set and the modem status interrupt is enabled, a modem status interrupt is generated.
  • Bit 4: This bit is the complement of the clear-to-send (CTS) input. When the ACE is in the diagnostic test mode (LOOP [MCR4] = 1), this bit is equal to the MCR bit 1 (RTS).
  • Bit 5: This bit is the complement of the data set ready (DSR) input. When the ACE is in the diagnostic test mode (LOOP [MCR4] = 1), this bit is equal to the MCR bit 0 (DTR).
  • Bit 6: This bit is the complement of the ring indicator (RI) input. When the ACE is in the diagnostic test mode (LOOP [MCR4] = 1), this bit is equal to the MCR bit 2 (OUT1).
  • Bit 7: This bit is the complement of the data carrier detect (DCD) input. When the ACE is in the diagnostic test mode (LOOP [MCR4] = 1), this bit is equal to the MCR bit 3 (OUT2).