ZHCSN84F January   2021  – October 2023 AM6411 , AM6412 , AM6421 , AM6422 , AM6441 , AM6442

PRODUCTION DATA  

  1.   1
  2. 特性
  3. 应用
  4. 说明
    1. 3.1 功能方框图
  5. Revision History
  6. Device Comparison
    1. 5.1 Related Products
  7. Terminal Configuration and Functions
    1. 6.1 Pin Diagrams
    2. 6.2 Pin Attributes
      1.      12
      2.      13
    3. 6.3 Signal Descriptions
      1.      15
      2. 6.3.1  ADC
        1. 6.3.1.1 MAIN Domain
          1.        18
      3. 6.3.2  CPSW3G
        1. 6.3.2.1 MAIN Domain
          1.        21
          2.        22
          3.        23
      4. 6.3.3  CPTS
        1. 6.3.3.1 MAIN Domain
          1.        26
          2.        27
      5. 6.3.4  DDRSS
        1. 6.3.4.1 MAIN Domain
          1.        30
      6. 6.3.5  ECAP
        1. 6.3.5.1 MAIN Domain
          1.        33
          2.        34
          3.        35
      7. 6.3.6  Emulation and Debug
        1. 6.3.6.1 MAIN Domain
          1.        38
        2. 6.3.6.2 MCU Domain
          1.        40
      8. 6.3.7  EPWM
        1. 6.3.7.1 MAIN Domain
          1.        43
          2.        44
          3.        45
          4.        46
          5.        47
          6.        48
          7.        49
          8.        50
          9.        51
          10.        52
      9. 6.3.8  EQEP
        1. 6.3.8.1 MAIN Domain
          1.        55
          2.        56
          3.        57
      10. 6.3.9  FSI
        1. 6.3.9.1 MAIN Domain
          1.        60
          2.        61
          3.        62
          4.        63
          5.        64
          6.        65
          7.        66
          8.        67
      11. 6.3.10 GPIO
        1. 6.3.10.1 MAIN Domain
          1.        70
          2.        71
        2. 6.3.10.2 MCU Domain
          1.        73
      12. 6.3.11 GPMC
        1. 6.3.11.1 MAIN Domain
          1.        76
      13. 6.3.12 I2C
        1. 6.3.12.1 MAIN Domain
          1.        79
          2.        80
          3.        81
          4.        82
        2. 6.3.12.2 MCU Domain
          1.        84
          2.        85
      14. 6.3.13 MCAN
        1. 6.3.13.1 MAIN Domain
          1.        88
          2.        89
      15. 6.3.14 MCSPI
        1. 6.3.14.1 MAIN Domain
          1.        92
          2.        93
          3.        94
          4.        95
          5.        96
        2. 6.3.14.2 MCU Domain
          1.        98
          2.        99
      16. 6.3.15 MDIO
        1. 6.3.15.1 MAIN Domain
          1.        102
      17. 6.3.16 MMC
        1. 6.3.16.1 MAIN Domain
          1.        105
          2.        106
      18. 6.3.17 OSPI
        1. 6.3.17.1 MAIN Domain
          1.        109
      19. 6.3.18 Power Supply
        1.       111
      20. 6.3.19 PRU_ICSSG
        1. 6.3.19.1 MAIN Domain
          1.        114
          2.        115
      21. 6.3.20 Reserved
        1.       117
      22. 6.3.21 SERDES
        1. 6.3.21.1 MAIN Domain
          1.        120
      23. 6.3.22 System and Miscellaneous
        1. 6.3.22.1 Boot Mode Configuration
          1. 6.3.22.1.1 MAIN Domain
            1.         124
        2. 6.3.22.2 Clock
          1. 6.3.22.2.1 MCU Domain
            1.         127
        3. 6.3.22.3 System
          1. 6.3.22.3.1 MAIN Domain
            1.         130
          2. 6.3.22.3.2 MCU Domain
            1.         132
        4. 6.3.22.4 VMON
          1.        134
      24. 6.3.23 TIMER
        1. 6.3.23.1 MAIN Domain
          1.        137
        2. 6.3.23.2 MCU Domain
          1.        139
      25. 6.3.24 UART
        1. 6.3.24.1 MAIN Domain
          1.        142
          2.        143
          3.        144
          4.        145
          5.        146
          6.        147
          7.        148
        2. 6.3.24.2 MCU Domain
          1.        150
          2.        151
      26. 6.3.25 USB
        1. 6.3.25.1 MAIN Domain
          1.        154
    4. 6.4 Pin Connectivity Requirements
  8. Specifications
    1. 7.1  Absolute Maximum Ratings
    2. 7.2  ESD Ratings
    3. 7.3  Power-On Hours (POH)
    4. 7.4  Recommended Operating Conditions
    5. 7.5  Operating Performance Points
    6. 7.6  Power Consumption Summary
    7. 7.7  Electrical Characteristics
      1. 7.7.1  I2C Open-Drain, and Fail-Safe (I2C OD FS) Electrical Characteristics
      2. 7.7.2  Fail-Safe Reset (FS RESET) Electrical Characteristics
      3. 7.7.3  High-Frequency Oscillator (HFOSC) Electrical Characteristics
      4. 7.7.4  eMMCPHY Electrical Characteristics
      5. 7.7.5  SDIO Electrical Characteristics
      6. 7.7.6  LVCMOS Electrical Characteristics
      7. 7.7.7  ADC12B Electrical Characteristics
      8. 7.7.8  USB2PHY Electrical Characteristics
      9. 7.7.9  SerDes PHY Electrical Characteristics
      10. 7.7.10 DDR Electrical Characteristics
    8. 7.8  VPP Specifications for One-Time Programmable (OTP) eFuses
      1. 7.8.1 Recommended Operating Conditions for OTP eFuse Programming
      2. 7.8.2 Hardware Requirements
      3. 7.8.3 Programming Sequence
      4. 7.8.4 Impact to Your Hardware Warranty
    9. 7.9  Thermal Resistance Characteristics
      1. 7.9.1 Thermal Resistance Characteristics
    10. 7.10 Timing and Switching Characteristics
      1. 7.10.1 Timing Parameters and Information
      2. 7.10.2 Power Supply Requirements
        1. 7.10.2.1 Power Supply Slew Rate Requirement
        2. 7.10.2.2 Power Supply Sequencing
          1. 7.10.2.2.1 Power-Up Sequencing
          2. 7.10.2.2.2 Power-Down Sequencing
      3. 7.10.3 System Timing
        1. 7.10.3.1 Reset Timing
        2. 7.10.3.2 Safety Signal Timing
        3. 7.10.3.3 Clock Timing
      4. 7.10.4 Clock Specifications
        1. 7.10.4.1 Input Clocks / Oscillators
          1. 7.10.4.1.1 MCU_OSC0 Internal Oscillator Clock Source
            1. 7.10.4.1.1.1 Load Capacitance
            2. 7.10.4.1.1.2 Shunt Capacitance
          2. 7.10.4.1.2 MCU_OSC0 LVCMOS Digital Clock Source
        2. 7.10.4.2 Output Clocks
        3. 7.10.4.3 PLLs
        4. 7.10.4.4 Recommended System Precautions for Clock and Control Signal Transitions
      5. 7.10.5 Peripherals
        1. 7.10.5.1  CPSW3G
          1. 7.10.5.1.1 CPSW3G MDIO Timing
          2. 7.10.5.1.2 CPSW3G RMII Timing
          3. 7.10.5.1.3 CPSW3G RGMII Timing
          4. 7.10.5.1.4 CPSW3G IOSETs
        2. 7.10.5.2  DDRSS
        3. 7.10.5.3  ECAP
        4. 7.10.5.4  EPWM
        5. 7.10.5.5  EQEP
        6. 7.10.5.6  FSI
        7. 7.10.5.7  GPIO
        8. 7.10.5.8  GPMC
          1. 7.10.5.8.1 GPMC and NOR Flash — Synchronous Mode
          2. 7.10.5.8.2 GPMC and NOR Flash — Asynchronous Mode
          3. 7.10.5.8.3 GPMC and NAND Flash — Asynchronous Mode
          4. 7.10.5.8.4 GPMC0 IOSETs
        9. 7.10.5.9  I2C
        10. 7.10.5.10 MCAN
        11. 7.10.5.11 MCSPI
          1. 7.10.5.11.1 MCSPI — Controller Mode
          2. 7.10.5.11.2 MCSPI — Peripheral Mode
        12. 7.10.5.12 MMCSD
          1. 7.10.5.12.1 MMC0 - eMMC Interface
            1. 7.10.5.12.1.1 Legacy SDR Mode
            2. 7.10.5.12.1.2 High Speed SDR Mode
            3. 7.10.5.12.1.3 High Speed DDR Mode
            4. 7.10.5.12.1.4 HS200 Mode
          2. 7.10.5.12.2 MMC1 - SD/SDIO Interface
            1. 7.10.5.12.2.1 Default Speed Mode
            2. 7.10.5.12.2.2 High Speed Mode
            3. 7.10.5.12.2.3 UHS–I SDR12 Mode
            4. 7.10.5.12.2.4 UHS–I SDR25 Mode
            5. 7.10.5.12.2.5 UHS–I SDR50 Mode
            6. 7.10.5.12.2.6 UHS–I DDR50 Mode
            7. 7.10.5.12.2.7 UHS–I SDR104 Mode
        13. 7.10.5.13 CPTS
        14. 7.10.5.14 OSPI
          1. 7.10.5.14.1 OSPI0 PHY Mode
            1. 7.10.5.14.1.1 OSPI0 With PHY Data Training
            2. 7.10.5.14.1.2 OSPI0 Without Data Training
              1. 7.10.5.14.1.2.1 OSPI0 PHY SDR Timing
              2. 7.10.5.14.1.2.2 OSPI0 PHY DDR Timing
          2. 7.10.5.14.2 OSPI0 Tap Mode
            1. 7.10.5.14.2.1 OSPI0 Tap SDR Timing
            2. 7.10.5.14.2.2 OSPI0 Tap DDR Timing
        15. 7.10.5.15 PCIe
        16. 7.10.5.16 PRU_ICSSG
          1. 7.10.5.16.1 PRU_ICSSG Programmable Real-Time Unit (PRU)
            1. 7.10.5.16.1.1 PRU_ICSSG PRU Direct Output Mode Timing
            2. 7.10.5.16.1.2 PRU_ICSSG PRU Parallel Capture Mode Timing
            3. 7.10.5.16.1.3 PRU_ICSSG PRU Shift Mode Timing
            4. 7.10.5.16.1.4 PRU_ICSSG PRU Sigma Delta and Peripheral Interface
              1. 7.10.5.16.1.4.1 PRU_ICSSG PRU Sigma Delta and Peripheral Interface Timing
          2. 7.10.5.16.2 PRU_ICSSG Pulse Width Modulation (PWM)
            1. 7.10.5.16.2.1 PRU_ICSSG PWM Timing
          3. 7.10.5.16.3 PRU_ICSSG Industrial Ethernet Peripheral (IEP)
            1. 7.10.5.16.3.1 PRU_ICSSG IEP Timing
          4. 7.10.5.16.4 PRU_ICSSG Universal Asynchronous Receiver Transmitter (UART)
            1. 7.10.5.16.4.1 PRU_ICSSG UART Timing
          5. 7.10.5.16.5 PRU_ICSSG Enhanced Capture Peripheral (ECAP)
            1. 7.10.5.16.5.1 PRU_ICSSG ECAP Timing
          6. 7.10.5.16.6 PRU_ICSSG RGMII, MII_RT, and Switch
            1. 7.10.5.16.6.1 PRU_ICSSG MDIO Timing
            2. 7.10.5.16.6.2 PRU_ICSSG MII Timing
            3. 7.10.5.16.6.3 PRU_ICSSG RGMII Timing
        17. 7.10.5.17 Timers
        18. 7.10.5.18 UART
        19. 7.10.5.19 USB
      6. 7.10.6 Emulation and Debug
        1. 7.10.6.1 Trace
        2. 7.10.6.2 JTAG
  9. Detailed Description
    1. 8.1 Overview
    2. 8.2 Processor Subsystems
      1. 8.2.1 Arm Cortex-A53 Subsystem
      2. 8.2.2 Arm Cortex-R5F Subsystem (R5FSS)
      3. 8.2.3 Arm Cortex-M4F (M4FSS)
    3. 8.3 Accelerators and Coprocessors
      1. 8.3.1 Programmable Real-Time Unit Subsystem and Industrial Communication Subsystem (PRU_ICSSG)
    4. 8.4 Other Subsystems
      1. 8.4.1 PDMA Controller
      2. 8.4.2 Peripherals
        1. 8.4.2.1  ADC
        2. 8.4.2.2  DCC
        3. 8.4.2.3  Dual Date Rate (DDR) External Memory Interface (DDRSS)
        4. 8.4.2.4  ECAP
        5. 8.4.2.5  EPWM
        6. 8.4.2.6  ELM
        7. 8.4.2.7  ESM
        8. 8.4.2.8  GPIO
        9. 8.4.2.9  EQEP
        10. 8.4.2.10 General-Purpose Memory Controller (GPMC)
        11. 8.4.2.11 I2C
        12. 8.4.2.12 MCAN
        13. 8.4.2.13 MCRC Controller
        14. 8.4.2.14 MCSPI
        15. 8.4.2.15 MMCSD
        16. 8.4.2.16 OSPI
        17. 8.4.2.17 Peripheral Component Interconnect Express (PCIe)
        18. 8.4.2.18 Serializer/Deserializer (SerDes) PHY
        19. 8.4.2.19 Real Time Interrupt (RTI/WWDT)
        20. 8.4.2.20 Dual Mode Timer (DMTIMER)
        21. 8.4.2.21 UART
        22. 8.4.2.22 Universal Serial Bus Subsystem (USBSS)
  10. Applications, Implementation, and Layout
    1. 9.1 Device Connection and Layout Fundamentals
      1. 9.1.1 Power Supply
        1. 9.1.1.1 Power Supply Designs
        2. 9.1.1.2 Power Distribution Network Implementation Guidance
      2. 9.1.2 External Oscillator
      3. 9.1.3 JTAG, EMU, and TRACE
      4. 9.1.4 Unused Pins
    2. 9.2 Peripheral- and Interface-Specific Design Information
      1. 9.2.1 DDR Board Design and Layout Guidelines
      2. 9.2.2 OSPI/QSPI/SPI Board Design and Layout Guidelines
        1. 9.2.2.1 No Loopback, Internal PHY Loopback, and Internal Pad Loopback
        2. 9.2.2.2 External Board Loopback
        3. 9.2.2.3 DQS (only available in Octal SPI devices)
      3. 9.2.3 USB VBUS Design Guidelines
      4. 9.2.4 System Power Supply Monitor Design Guidelines
      5. 9.2.5 High Speed Differential Signal Routing Guidance
      6. 9.2.6 Thermal Solution Guidance
    3. 9.3 Clock Routing Guidelines
      1. 9.3.1 Oscillator Routing
  11. 10Device and Documentation Support
    1. 10.1 Device Nomenclature
      1. 10.1.1 Standard Package Symbolization
      2. 10.1.2 Device Naming Convention
    2. 10.2 Tools and Software
    3. 10.3 Documentation Support
    4. 10.4 支持资源
    5. 10.5 Trademarks
    6. 10.6 静电放电警告
    7. 10.7 术语表
  12. 11Mechanical, Packaging, and Orderable Information
    1. 11.1 Packaging Information

封装选项

请参考 PDF 数据表获取器件具体的封装图。

机械数据 (封装 | 引脚)
  • ALV|441
散热焊盘机械数据 (封装 | 引脚)
订购信息

Pin Connectivity Requirements

This section describes connectivity requirements for package balls that have specific connectivity requirements and unused package balls.

Note:

All power balls must be supplied with the voltages specified in the Recommended Operating Conditions section, unless otherwise specified.

Note:

For additional clarification, "leave unconnected" or "no connect" (NC) means no signal traces can be connected to these device ball numbers.

Table 6-80 Connectivity Requirements
BALL NUMBER BALL NAME CONNECTION REQUIREMENTS
A20
D11
MCU_SAFETY_ERRORn
TRSTn
Each of these balls must be connected to VSS through separate external pull resistors to ensure the inputs associated with these balls are held to a valid logic low level if a PCB signal trace is connected and not actively driven by an attached device. The internal pull-down can be used to hold a valid logic low level if no PCB signal trace is connected to the ball.
D10
E10
B12
E18
B11
C11
C12
EMU0
EMU1
MCU_RESETz
RESET_REQz
TCK
TDI
TMS
Each of these balls must be connected to the corresponding power supply(1) through separate external pull resistors to ensure the inputs associated with these balls are held to a valid logic high level if a PCB signal trace is connected and not actively driven by an attached device. The internal pull-up can be used to hold a valid logic high level if no PCB signal trace is connected to the ball.
A18
B18
E9
A10
I2C0_SCL
I2C0_SDA
MCU_I2C0_SCL
MCU_I2C0_SDA
Each of these balls must be connected to the corresponding power supply(1) through separate external pull resistors to ensure the inputs associated with these balls are held to a valid logic high level.
T20
U21
T18
U20
U18
U19
V20
V21
V19
T17
R16
W20
W21
V18
Y21
Y20
GPMC0_AD0
GPMC0_AD1
GPMC0_AD2
GPMC0_AD3
GPMC0_AD4
GPMC0_AD5
GPMC0_AD6
GPMC0_AD7
GPMC0_AD8
GPMC0_AD9
GPMC0_AD10
GPMC0_AD11
GPMC0_AD12
GPMC0_AD13
GPMC0_AD14
GPMC0_AD15
Each of these balls must be connected to the corresponding power supply(1) or VSS through separate external pull resistors to ensure the inputs associated with these balls are held to a valid logic high or low level as appropriate to select the desired device boot mode.
J13
G20
F20
E21,
D20
G21
F21
F19
E20
J15
J16
VDDA_ADC
ADC0_AIN0
ADC0_AIN1
ADC0_AIN2
ADC0_AIN3
ADC0_AIN4
ADC0_AIN5
ADC0_AIN6
ADC0_AIN7
ADC0_REFP
ADC0_REFN
If the entire ADC0 is not used, each of these balls must be connected directly to VSS.
G20
F20
E21,
D20
G21
F21
F19
E20
ADC0_AIN0
ADC0_AIN1
ADC0_AIN2
ADC0_AIN3
ADC0_AIN4
ADC0_AIN5
ADC0_AIN6
ADC0_AIN7
Any unused ADC0_AIN[7:0] ball must be pulled to VSS through a resistor or connected directly to VSS when VDDA_ADC is connected to a power source.
F7
G6
H7
J6,
K7
L6
J8
VDDS_DDR
VDDS_DDR
VDDS_DDR
VDDS_DDR
VDDS_DDR
VDDS_DDR
VDDS_DDR_C
If DDRSS0 is not used, each of these balls must be connected directly to VSS.
H2
H1
J5
K5
F6
H4
D2
C5
E2
D4
D3
F2
J2
L5
J3
J4
K3
J1
M5
K4
G4
G5
G2
H3
H5
F1
E1
F4
F3
E3
E4
B2
M2
A3
A2
B5
A4
B3
C4
C2
B4
N5
L4
L2
M3
N4
N3
M4
N2
C1
B1
N1
M1
E5
F5
D5
DDR0_ACT_n
DDR0_ALERT_n
DDR0_CAS_n
DDR0_PAR
DDR0_RAS_n
DDR0_WE_n
DDR0_A0
DDR0_A1
DDR0_A2
DDR0_A3
DDR0_A4
DDR0_A5
DDR0_A6
DDR0_A7
DDR0_A8
DDR0_A9
DDR0_A10
DDR0_A11
DDR0_A12
DDR0_A13
DDR0_BA0
DDR0_BA1
DDR0_BG0
DDR0_BG1
DDR0_CAL0
DDR0_CK0
DDR0_CK0_n
DDR0_CKE0
DDR0_CKE1
DDR0_CS0_n
DDR0_CS1_n
DDR0_DM0
DDR0_DM1
DDR0_DQ0
DDR0_DQ1
DDR0_DQ2
DDR0_DQ3
DDR0_DQ4
DDR0_DQ5
DDR0_DQ6
DDR0_DQ7
DDR0_DQ8
DDR0_DQ9
DDR0_DQ10
DDR0_DQ11
DDR0_DQ12
DDR0_DQ13
DDR0_DQ14
DDR0_DQ15
DDR0_DQS0
DDR0_DQS0_n
DDR0_DQS1
DDR0_DQS1_n
DDR0_ODT0
DDR0_ODT1
DDR0_RESET0_n
If DDRSS0 is not used, leave unconnected.Note: The DDR0 pins in this list can only be left unconnected when VDDS_DDR and VDDS_DDR_C are connected to VSS. The DDR0 pins must be connected as defined in the AM64x\AM243x DDR Board Design and Layout Guidelines, when VDDS_DDR and VDDS_DDR_C are connected to a power source.
K13
H14
VDD_MMC0
VDD_DLL_MMC0
If MMC0 is not used, each of these balls must be connected to the same power source as VDD_CORE.
K14 VDDS_MMC0 If MMC0 is not used, each of these balls must be connected to any 1.8-V power source that does not violate device power supply sequencing requirements.
F18
G18
J21
G19
K20
J20
J18
J17
H17
H19
H18
G17
MMC0_CALPAD
MMC0_CLK
MMC0_CMD
MMC0_DS
MMC0_DAT0
MMC0_DAT1
MMC0_DAT2
MMC0_DAT3
MMC0_DAT4
MMC0_DAT5
MMC0_DAT6
MMC0_DAT7
If MMC0 is not used, each of these balls must be left unconnected.
H15
K15
VDDA_3P3_SDIO
CAP_VDDSHV_MMC1
If SDIO_LDO is not used to power VDDSHV5, each of these balls must be connected directly to VSS.
P12
P13
P11
R14
VDDA_0P85_SERDES0
VDDA_0P85_SERDES0
VDDA_0P85_SERDES0_C
VDDA_1P8_SERDES0
If SERDES0 is not used and the device boundary scan function is required, each of these balls must be connected to valid power sources.If SERDES0 is not used and the device boundary scan function is not required, each of these balls can alternatively be connected directly to VSS.
T13
W16
W17
Y15
Y16
AA16
AA17
SERDES0_REXT
SERDES0_REFCLK0N
SERDES0_REFCLK0P
SERDES0_RX0_N
SERDES0_RX0_P
SERDES0_TX0_N
SERDES0_TX0_P
If SERDES0 is not used, leave unconnected.Note: The SERDES0_REXT pin can only be left unconnected when VDDA_0P85_SERDES0, VDDA_0P85_SERDES0_C, and VDDA_1P8_SERDES0 are connected to VSS. The SERDES0_REXT pin must be connected to VSS through the appropriate external resistor when VDDA_0P85_SERDES0, VDDA_0P85_SERDES0_C, and VDDA_1P8_SERDES0 are connected to power sources.
T12
R15
R13
VDDA_0P85_USB0
VDDA_1P8_USB0
VDDA_3P3_USB0
If USB0 is not used, each of these balls must be connected directly to VSS.
AA20
AA19
U16
U17
T14
USB0_DM
USB0_DP
USB0_ID
USB0_RCALIB
USB0_VBUS
If USB0 is not used, leave unconnected.Note: The USB0_RCALIB pin can only be left unconnected when VDDA_0P85_USB0, VDDA_1P8_USB0, and VDDA_3P3_USB0 are connected to VSS. The USB0_RCALIB pin must be connected to VSS through the appropriate external resistor when VDDA_0P85_USB0, VDDA_1P8_USB0, and VDDA_3P3_USB0 are connected to power sources.
K10 VMON_VSYS If VMON_VSYS is not used, this ball must be connected directly to VSS.
K16
E12
F13
F14
VMON_1P8_MCU
VMON_1P8_SOC
VMON_3P3_MCU
VMON_3P3_SOC
If VMON_1P8_MCU, VMON_1P8_SOC, VMON_3P3_MCU, and VMON_3P3_SOC are not used to monitor the MCU and SOC power rails, these balls must still be connected to their respective 1.8-V and 3.3-V power rails.
To determine which power supply is associated with any IO, see the POWER column of the Pin Attributes table.

Note:

Internal pull resistors are weak and may not source enough current to maintain a valid logic level for some operating conditions. This can be the case when connected to components with leakage to the opposite logic level, or when external noise sources couple to signal traces attached to balls which are only pulled to a valid logic level by the internal resistor. Therefore, external pull resistors are recommended to hold a valid logic level on balls with external connections.

Many of the device IOs are turned off by default and external pull resistors may be required to hold inputs of any attached device in a valid logic state until software initializes the respective IOs. The state of configurable device IOs are defined in the BALL STATE DURING RESET RX/TX/PULL and BALL STATE AFTER RESET RX/TX/PULL columns of the Pin Attributes table. Any IO with its input buffer (RX) turned off is allowed to float without damaging the device. However, any IO with its input buffer (RX) turned on shall never be allowed to float to any potential between VILSS and VIHSS. The input buffer can enter a high-current state which could damage the IO cell if allowed to float between these levels.