SBAS883A February   2018  – June 2018 OPT3101

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Requirements
    7. 6.7 Typical Characteristics
      1. 6.7.1 Continuous Mode
      2. 6.7.2 Monoshot Mode
      3. 6.7.3 Monoshot Mode With Internal LDO
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Timing Generator
        1. 7.3.1.1 Continuous Operating Mode
        2. 7.3.1.2 Monoshot Mode
        3. 7.3.1.3 Non-HDR Mode
        4. 7.3.1.4 Auto HDR Mode
        5. 7.3.1.5 Multi Channel Mode
      2. 7.3.2  AFE
      3. 7.3.3  Ambient Cancellation
      4. 7.3.4  Oscillator
      5. 7.3.5  CLKGEN
      6. 7.3.6  Illumination Driver
      7. 7.3.7  Depth Engine
      8. 7.3.8  Output Data
      9. 7.3.9  General Purpose I/O
      10. 7.3.10 Temperature Sensor
      11. 7.3.11 On-Chip Regulator
      12. 7.3.12 Sequencer
        1. 7.3.12.1 Interrupt Output
        2. 7.3.12.2 Super-HDR Mode Using Sequencer
    4. 7.4 Programming
      1. 7.4.1 I2C Slave
      2. 7.4.2 I2C Master
        1. 7.4.2.1 External Temperature Sensor
        2. 7.4.2.2 External EEPROM
        3. 7.4.2.3 External EEPROM Programming
    5. 7.5 Register Maps
      1. 7.5.1 Serial Interface Register Map
        1. 7.5.1.1 Register Descriptions
          1. 7.5.1.1.1   Register 0h (Address = 0h) [reset = 0h]
            1. Table 31. Register 00 Field Descriptions
          2. 7.5.1.1.2   Register 1h (Address = 1h) [reset = 120140h]
            1. Table 32. Register 01 Field Descriptions
          3. 7.5.1.1.3   Register 2h (Address = 2h) [reset = 92A4C8h]
            1. Table 33. Register 02 Field Descriptions
          4. 7.5.1.1.4   Register 3h (Address = 3h) [reset = 800000h]
            1. Table 34. Register 03 Field Descriptions
          5. 7.5.1.1.5   Register 4h (Address = 4h) [reset = 17h]
            1. Table 35. Register 04 Field Descriptions
          6. 7.5.1.1.6   Register 5h (Address = 5h) [reset = 80000h]
            1. Table 36. Register 05 Field Descriptions
          7. 7.5.1.1.7   Register 7h (Address = 7h) [reset = 0h]
            1. Table 37. Register 07 Field Descriptions
          8. 7.5.1.1.8   Register 8h (Address = 8h) [reset = 0h]
            1. Table 38. Register 08 Field Descriptions
          9. 7.5.1.1.9   Register 9h (Address = 9h) [reset = 0h]
            1. Table 39. Register 09 Field Descriptions
          10. 7.5.1.1.10  Register Ah (Address = Ah) [reset = 0h]
            1. Table 40. Register 0A Field Descriptions
          11. 7.5.1.1.11  Register Bh (Address = Bh) [reset = FC009h]
            1. Table 41. Register 0B Field Descriptions
          12. 7.5.1.1.12  Register Ch (Address = Ch) [reset = 0h]
            1. Table 42. Register 0C Field Descriptions
          13. 7.5.1.1.13  Register Dh (Address = Dh) [reset = 6000h]
            1. Table 43. Register 0D Field Descriptions
          14. 7.5.1.1.14  Register Fh (Address = Fh) [reset = 144C4Bh]
            1. Table 44. Register 0F Field Descriptions
          15. 7.5.1.1.15  Register 10h (Address = 10h) [reset = 4000h]
            1. Table 45. Register 10 Field Descriptions
          16. 7.5.1.1.16  Register 11h (Address = 11h) [reset = 0h]
            1. Table 46. Register 11 Field Descriptions
          17. 7.5.1.1.17  Register 13h (Address = 13h) [reset = 0h]
            1. Table 47. Register 13 Field Descriptions
          18. 7.5.1.1.18  Register 14h (Address = 14h) [reset = 0h]
            1. Table 48. Register 14 Field Descriptions
          19. 7.5.1.1.19  Register 15h (Address = 15h) [reset = 101063h]
            1. Table 49. Register 15 Field Descriptions
          20. 7.5.1.1.20  Register 16h (Address = 16h) [reset = 400100h]
            1. Table 50. Register 16 Field Descriptions
          21. 7.5.1.1.21  Register 17h (Address = 17h) [reset = 0h]
            1. Table 51. Register 17 Field Descriptions
          22. 7.5.1.1.22  Register 18h (Address = 18h) [reset = 0h]
            1. Table 52. Register 18 Field Descriptions
          23. 7.5.1.1.23  Register 19h (Address = 19h) [reset = 0h]
            1. Table 53. Register 19 Field Descriptions
          24. 7.5.1.1.24  Register 1Ah (Address = 1Ah) [reset = 0h]
            1. Table 54. Register 1A Field Descriptions
          25. 7.5.1.1.25  Register 1Bh (Address = 1Bh) [reset = 0h]
            1. Table 55. Register 1B Field Descriptions
          26. 7.5.1.1.26  Register 1Ch (Address = 1Ch) [reset = 0h]
            1. Table 56. Register 1C Field Descriptions
          27. 7.5.1.1.27  Register 1Dh (Address = 1Dh) [reset = 0h]
            1. Table 57. Register 1D Field Descriptions
          28. 7.5.1.1.28  Register 1Eh (Address = 1Eh) [reset = 0h]
            1. Table 58. Register 1E Field Descriptions
          29. 7.5.1.1.29  Register 26h (Address = 26h) [reset = 4000Fh]
            1. Table 59. Register 26 Field Descriptions
          30. 7.5.1.1.30  Register 27h (Address = 27h) [reset = 26AC18h]
            1. Table 60. Register 27 Field Descriptions
          31. 7.5.1.1.31  Register 29h (Address = 29h) [reset = 3F0FC3h]
            1. Table 61. Register 29 Field Descriptions
          32. 7.5.1.1.32  Register 2Ah (Address = 2Ah) [reset = 784920h]
            1. Table 62. Register 2A Field Descriptions
          33. 7.5.1.1.33  Register 2Bh (Address = 2Bh) [reset = 6000h]
            1. Table 63. Register 2B Field Descriptions
          34. 7.5.1.1.34  Register 2Ch (Address = 2Ch) [reset = 800h]
            1. Table 64. Register 2C Field Descriptions
          35. 7.5.1.1.35  Register 2Dh (Address = 2Dh) [reset = 0h]
            1. Table 65. Register 2D Field Descriptions
          36. 7.5.1.1.36  Register 2Eh (Address = 2Eh) [reset = 8001A0h]
            1. Table 66. Register 2E Field Descriptions
          37. 7.5.1.1.37  Register 2Fh (Address = 2Fh) [reset = 0h]
            1. Table 67. Register 2F Field Descriptions
          38. 7.5.1.1.38  Register 30h (Address = 30h) [reset = 0h]
            1. Table 68. Register 30 Field Descriptions
          39. 7.5.1.1.39  Register 31h (Address = 31h) [reset = 0h]
            1. Table 69. Register 31 Field Descriptions
          40. 7.5.1.1.40  Register 32h (Address = 32h) [reset = 0h]
            1. Table 70. Register 32 Field Descriptions
          41. 7.5.1.1.41  Register 33h (Address = 33h) [reset = 0h]
            1. Table 71. Register 33 Field Descriptions
          42. 7.5.1.1.42  Register 34h (Address = 34h) [reset = 0h]
            1. Table 72. Register 34 Field Descriptions
          43. 7.5.1.1.43  Register 35h (Address = 35h) [reset = 0h]
            1. Table 73. Register 35 Field Descriptions
          44. 7.5.1.1.44  Register 36h (Address = 36h) [reset = 0h]
            1. Table 74. Register 36 Field Descriptions
          45. 7.5.1.1.45  Register 37h (Address = 37h) [reset = 0h]
            1. Table 75. Register 37 Field Descriptions
          46. 7.5.1.1.46  Register 38h (Address = 38h) [reset = 0h]
            1. Table 76. Register 38 Field Descriptions
          47. 7.5.1.1.47  Register 39h (Address = 39h) [reset = 0h]
            1. Table 77. Register 39 Field Descriptions
          48. 7.5.1.1.48  Register 3Ah (Address = 3Ah) [reset = 0h]
            1. Table 78. Register 3A Field Descriptions
          49. 7.5.1.1.49  Register 3Bh (Address = 3Bh) [reset = 0h]
            1. Table 79. Register 3B Field Descriptions
          50. 7.5.1.1.50  Register 3Ch (Address = 3Ch) [reset = 0h]
            1. Table 80. Register 3C Field Descriptions
          51. 7.5.1.1.51  Register 3Dh (Address = 3Dh) [reset = 0h]
            1. Table 81. Register 3D Field Descriptions
          52. 7.5.1.1.52  Register 3Eh (Address = 3Eh) [reset = 0h]
            1. Table 82. Register 3E Field Descriptions
          53. 7.5.1.1.53  Register 3Fh (Address = 3Fh) [reset = 0h]
            1. Table 83. Register 3F Field Descriptions
          54. 7.5.1.1.54  Register 40h (Address = 40h) [reset = 2021E0h]
            1. Table 84. Register 40 Field Descriptions
          55. 7.5.1.1.55  Register 41h (Address = 41h) [reset = 10h]
            1. Table 85. Register 41 Field Descriptions
          56. 7.5.1.1.56  Register 42h (Address = 42h) [reset = 0h]
            1. Table 86. Register 42 Field Descriptions
          57. 7.5.1.1.57  Register 43h (Address = 43h) [reset = 81h]
            1. Table 87. Register 43 Field Descriptions
          58. 7.5.1.1.58  Register 44h (Address = 44h) [reset = 0h]
            1. Table 88. Register 44 Field Descriptions
          59. 7.5.1.1.59  Register 45h (Address = 45h) [reset = 0h]
            1. Table 89. Register 45 Field Descriptions
          60. 7.5.1.1.60  Register 46h (Address = 46h) [reset = 0h]
            1. Table 90. Register 46 Field Descriptions
          61. 7.5.1.1.61  Register 47h (Address = 47h) [reset = 800800h]
            1. Table 91. Register 47 Field Descriptions
          62. 7.5.1.1.62  Register 48h (Address = 48h) [reset = 0h]
            1. Table 92. Register 48 Field Descriptions
          63. 7.5.1.1.63  Register 49h (Address = 49h) [reset = 0h]
            1. Table 93. Register 49 Field Descriptions
          64. 7.5.1.1.64  Register 4Ah (Address = 4Ah) [reset = 0h]
            1. Table 94. Register 4A Field Descriptions
          65. 7.5.1.1.65  Register 4Bh (Address = 4Bh) [reset = 407h]
            1. Table 95. Register 4B Field Descriptions
          66. 7.5.1.1.66  Register 4Ch (Address = 4Ch) [reset = F23Eh]
            1. Table 96. Register 4C Field Descriptions
          67. 7.5.1.1.67  Register 4Dh (Address = 4Dh) [reset = 1144h]
            1. Table 97. Register 4D Field Descriptions
          68. 7.5.1.1.68  Register 4Eh (Address = 4Eh) [reset = F881h]
            1. Table 98. Register 4E Field Descriptions
          69. 7.5.1.1.69  Register 50h (Address = 50h) [reset = 200100h]
            1. Table 99. Register 50 Field Descriptions
          70. 7.5.1.1.70  Register 51h (Address = 51h) [reset = 0h]
            1. Table 100. Register 51 Field Descriptions
          71. 7.5.1.1.71  Register 52h (Address = 52h) [reset = 0h]
            1. Table 101. Register 52 Field Descriptions
          72. 7.5.1.1.72  Register 53h (Address = 53h) [reset = 0h]
            1. Table 102. Register 53 Field Descriptions
          73. 7.5.1.1.73  Register 54h (Address = 54h) [reset = 0h]
            1. Table 103. Register 54 Field Descriptions
          74. 7.5.1.1.74  Register 55h (Address = 55h) [reset = 0h]
            1. Table 104. Register 55 Field Descriptions
          75. 7.5.1.1.75  Register 56h (Address = 56h) [reset = 0h]
            1. Table 105. Register 56 Field Descriptions
          76. 7.5.1.1.76  Register 57h (Address = 57h) [reset = 0h]
            1. Table 106. Register 57 Field Descriptions
          77. 7.5.1.1.77  Register 58h (Address = 58h) [reset = 0h]
            1. Table 107. Register 58 Field Descriptions
          78. 7.5.1.1.78  Register 59h (Address = 59h) [reset = 0h]
            1. Table 108. Register 59 Field Descriptions
          79. 7.5.1.1.79  Register 5Ah (Address = 5Ah) [reset = 0h]
            1. Table 109. Register 5A Field Descriptions
          80. 7.5.1.1.80  Register 5Bh (Address = 5Bh) [reset = 0h]
            1. Table 110. Register 5B Field Descriptions
          81. 7.5.1.1.81  Register 5Ch (Address = 5Ch) [reset = 0h]
            1. Table 111. Register 5C Field Descriptions
          82. 7.5.1.1.82  Register 5Dh (Address = 5Dh) [reset = 0h]
            1. Table 112. Register 5D Field Descriptions
          83. 7.5.1.1.83  Register 5Eh (Address = 5Eh) [reset = 0h]
            1. Table 113. Register 5E Field Descriptions
          84. 7.5.1.1.84  Register 5Fh (Address = 5Fh) [reset = 0h]
            1. Table 114. Register 5F Field Descriptions
          85. 7.5.1.1.85  Register 60h (Address = 60h) [reset = 0h]
            1. Table 115. Register 60 Field Descriptions
          86. 7.5.1.1.86  Register 61h (Address = 61h) [reset = 0h]
            1. Table 116. Register 61 Field Descriptions
          87. 7.5.1.1.87  Register 64h (Address = 64h) [reset = 280C00h]
            1. Table 117. Register 64 Field Descriptions
          88. 7.5.1.1.88  Register 65h (Address = 65h) [reset = 0h]
            1. Table 118. Register 65 Field Descriptions
          89. 7.5.1.1.89  Register 6Eh (Address = 6Eh) [reset = 20000h]
            1. Table 119. Register 6E Field Descriptions
          90. 7.5.1.1.90  Register 71h (Address = 71h) [reset = 0h]
            1. Table 120. Register 71 Field Descriptions
          91. 7.5.1.1.91  Register 72h (Address = 72h) [reset = C0h]
            1. Table 121. Register 72 Field Descriptions
          92. 7.5.1.1.92  Register 76h (Address = 76h) [reset = 0h]
            1. Table 122. Register 76 Field Descriptions
          93. 7.5.1.1.93  Register 77h (Address = 77h) [reset = 0h]
            1. Table 123. Register 77 Field Descriptions
          94. 7.5.1.1.94  Register 78h (Address = 78h) [reset = 0h]
            1. Table 124. Register 78 Field Descriptions
          95. 7.5.1.1.95  Register 79h (Address = 79h) [reset = 1h]
            1. Table 125. Register 79 Field Descriptions
          96. 7.5.1.1.96  Register 7Ah (Address = 7Ah) [reset = 0h]
            1. Table 126. Register 7A Field Descriptions
          97. 7.5.1.1.97  Register 80h (Address = 80h) [reset = 4E1Eh]
            1. Table 127. Register 80 Field Descriptions
          98. 7.5.1.1.98  Register 83h (Address = 83h) [reset = D0h]
            1. Table 128. Register 83 Field Descriptions
          99. 7.5.1.1.99  Register 84h (Address = 84h) [reset = D8h]
            1. Table 129. Register 84 Field Descriptions
          100. 7.5.1.1.100 Register 85h (Address = 85h) [reset = 20h]
            1. Table 130. Register 85 Field Descriptions
          101. 7.5.1.1.101 Register 86h (Address = 86h) [reset = 28h]
            1. Table 131. Register 86 Field Descriptions
          102. 7.5.1.1.102 Register 87h (Address = 87h) [reset = 2454h]
            1. Table 132. Register 87 Field Descriptions
          103. 7.5.1.1.103 Register 88h (Address = 88h) [reset = 2648h]
            1. Table 133. Register 88 Field Descriptions
          104. 7.5.1.1.104 Register 89h (Address = 89h) [reset = 3E8h]
            1. Table 134. Register 89 Field Descriptions
          105. 7.5.1.1.105 Register 8Ah (Address = 8Ah) [reset = 1F40h]
            1. Table 135. Register 8A Field Descriptions
          106. 7.5.1.1.106 Register 8Fh (Address = 8Fh) [reset = 0h]
            1. Table 136. Register 8F Field Descriptions
          107. 7.5.1.1.107 Register 90h (Address = 90h) [reset = 2134h]
            1. Table 137. Register 90 Field Descriptions
          108. 7.5.1.1.108 Register 91h (Address = 91h) [reset = 2134h]
            1. Table 138. Register 91 Field Descriptions
          109. 7.5.1.1.109 Register 92h (Address = 92h) [reset = 2EE0h]
            1. Table 139. Register 92 Field Descriptions
          110. 7.5.1.1.110 Register 93h (Address = 93h) [reset = 0h]
            1. Table 140. Register 93 Field Descriptions
          111. 7.5.1.1.111 Register 94h (Address = 94h) [reset = FFFFh]
            1. Table 141. Register 94 Field Descriptions
          112. 7.5.1.1.112 Register 97h (Address = 97h) [reset = 0h]
            1. Table 142. Register 97 Field Descriptions
          113. 7.5.1.1.113 Register 98h (Address = 98h) [reset = 0h]
            1. Table 143. Register 98 Field Descriptions
          114. 7.5.1.1.114 Register 99h (Address = 99h) [reset = 1h]
            1. Table 144. Register 99 Field Descriptions
          115. 7.5.1.1.115 Register 9Ch (Address = 9Ch) [reset = FFF000h]
            1. Table 145. Register 9C Field Descriptions
          116. 7.5.1.1.116 Register 9Dh (Address = 9Dh) [reset = 0h]
            1. Table 146. Register 9D Field Descriptions
          117. 7.5.1.1.117 Register 9Eh (Address = 9Eh) [reset = 0h]
            1. Table 147. Register 9E Field Descriptions
          118. 7.5.1.1.118 Register 9Fh (Address = 9Fh) [reset = 0h]
            1. Table 148. Register 9F Field Descriptions
          119. 7.5.1.1.119 Register A0h (Address = A0h) [reset = 2198h]
            1. Table 149. Register A0 Field Descriptions
          120. 7.5.1.1.120 Register A2h (Address = A2h) [reset = 0h]
            1. Table 150. Register A2 Field Descriptions
          121. 7.5.1.1.121 Register A3h (Address = A3h) [reset = 0h]
            1. Table 151. Register A3 Field Descriptions
          122. 7.5.1.1.122 Register A4h (Address = A4h) [reset = 0h]
            1. Table 152. Register A4 Field Descriptions
          123. 7.5.1.1.123 Register A5h (Address = A5h) [reset = 0h]
            1. Table 153. Register A5 Field Descriptions
          124. 7.5.1.1.124 Register A6h (Address = A6h) [reset = 0h]
            1. Table 154. Register A6 Field Descriptions
          125. 7.5.1.1.125 Register A7h (Address = A7h) [reset = 0h]
            1. Table 155. Register A7 Field Descriptions
          126. 7.5.1.1.126 Register A8h (Address = A8h) [reset = 0h]
            1. Table 156. Register A8 Field Descriptions
          127. 7.5.1.1.127 Register A9h (Address = A9h) [reset = 0h]
            1. Table 157. Register A9 Field Descriptions
          128. 7.5.1.1.128 Register AAh (Address = AAh) [reset = 0h]
            1. Table 158. Register AA Field Descriptions
          129. 7.5.1.1.129 Register ABh (Address = ABh) [reset = 0h]
            1. Table 159. Register AB Field Descriptions
          130. 7.5.1.1.130 Register ACh (Address = ACh) [reset = 0h]
            1. Table 160. Register AC Field Descriptions
          131. 7.5.1.1.131 Register ADh (Address = ADh) [reset = 0h]
            1. Table 161. Register AD Field Descriptions
          132. 7.5.1.1.132 Register AEh (Address = AEh) [reset = 0h]
            1. Table 162. Register AE Field Descriptions
          133. 7.5.1.1.133 Register AFh (Address = AFh) [reset = 0h]
            1. Table 163. Register AF Field Descriptions
          134. 7.5.1.1.134 Register B0h (Address = B0h) [reset = 0h]
            1. Table 164. Register B0 Field Descriptions
          135. 7.5.1.1.135 Register B1h (Address = B1h) [reset = 0h]
            1. Table 165. Register B1 Field Descriptions
          136. 7.5.1.1.136 Register B2h (Address = B2h) [reset = 0h]
            1. Table 166. Register B2 Field Descriptions
          137. 7.5.1.1.137 Register B4h (Address = B4h) [reset = 0h]
            1. Table 167. Register B4 Field Descriptions
          138. 7.5.1.1.138 Register B5h (Address = B5h) [reset = 0h]
            1. Table 168. Register B5 Field Descriptions
          139. 7.5.1.1.139 Register B8h (Address = B8h) [reset = 7FDFFh]
            1. Table 169. Register B8 Field Descriptions
          140. 7.5.1.1.140 Register B8h (Address = B9h) [reset = 1FFh]
            1. Table 170. Register B9 Field Descriptions
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Sample Rate
        2. 8.2.2.2 Photodiode and LED
        3. 8.2.2.3 Ambient Support
        4. 8.2.2.4 Distance Accuracy
        5. 8.2.2.5 Supply Voltage
      3. 8.2.3 Application Curves
    3. 8.3 Initialization Set Up
  9. 9 Power Supply Recommendations
    1. 9.1 System With Off-Chip 1.8-V Regulator
    2. 9.2 System With On-Chip 1.8-V Regulator
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

7.5.1.1.14 Register Fh (Address = Fh) [reset = 144C4Bh]

Figure 42. Register Fh
23 22 21 20 19 18 17 16
EN_FREQ_CORR EN_FLOOP EN_AUTO_FREQ_COUNT SYS_CLK_DIVIDER START_FREQ_CALIB
R/W - 0h R/W - 0h R/W - 0h R/W - Ah R/W - 0h
15 14 13 12 11 10 9 8
RESERVED REF_COUNT_LIMIT
R/W - 0h R/W - 4Ch
7 6 5 4 3 2 1 0
REF_COUNT_LIMIT
R/W - 4Bh

Table 44. Register 0F Field Descriptions

Bit Field Type Reset Description
23 EN_FREQ_CORR R/W 0h Enable frequency correction for the phase output.
0: Frequency correction disabled | 1: Frequency correction enabled
22 EN_FLOOP R/W 0h Enables the frequency calibration block.
0: Disable frequency calibration block | 1: Enable frequency calibration block
21 EN_AUTO_FREQ_COUNT R/W 0h Determines the value to be used for frequency correction.
0 – On-chip trimmed value | 1 – Measured value from frequency calibration
20:17 SYS_CLK_DIVIDER R/W Ah Programs the system-clock divider for frequency calibration. This register should be adjusted to get it closer to the external reference frequency connected to GP2 pin.
SYS_CLK_DIVIDER = round(log2(40 × 106 / fEXT))
16 START_FREQ_CALIB R/W 0h Setting this bit to 1 starts the frequency calibration.
15 RESERVED R/W 0h Always read or write 0h.
14:0 REF_COUNT_LIMIT R/W 4C4Bh This sets the limit for ref-clock count.
REF_COUNT_LIMIT = (40 × 106 / 2SYS_CLK_DIVIDER) / fEXT