FT24C16A-ETR-T

Fremont Micro Devices FT24C16A-Exx Two-Wire Serial EEPROM 16K (8-bit wide) FEATURES  Low voltage and low power operations:  16 bytes page write mode.  Partial page write operation allowed.  Internally organized: 2048× 8 (16K).  Standard 2-wire bi-directional serial interface.  Schmitt trigger, filtered inputs for noise protection.  Self-timed programming cycle (5ms maximum).  1 MHz (2.5-5V), 400 kHz (1.8V) Compatibility.  Automatic erase before write operation.  Write protect pin for hardware data protection.  High reliability: typically 1,000,000 cycles endurance.  100 years data retention.  Standard 8-pin DIP/SOP/MSOP/TSSOP/DFN and 5-pin SOT-23/TSOT-23 Pb-free packages.  FT24C16A: VCC = 1.8V to 5.5V, Industrial temperature range (-40℃ to 85℃). DESCRIPTION The FT24C16A is 16,384 bits of serial Electrical Erasable and Programmable Read Only Memory, commonly known as EEPROM. They are organized as 2,048 words of 8 bits (1 byte) each. The devices are fabricated with proprietary advanced CMOS process for low power and low voltage applications. These devices are available in standard 8-lead DIP, 8-lead SOP, 8-lead MSOP, 8-lead TSSOP, 8-lead DFN and 5-lead SOT-23/TSOT-23 packages. A standard 2-wire serial interface is used to address all read and write functions. Our extended VCC range (1.8V to 5.5V) devices enables wide spectrum of applications. © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page1 Fremont Micro Devices FT24C16A-Exx PIN CONFIGURATION Pin Name Pin Function SDA SCL WP Serial Data Input / Open Drain Output Serial Clock Input Write Protect VCC GND NC Power Supply Ground No-Connect Table 1 All these packaging types come in conventional or Pb-free certified. Figure 1: Package types ABSOLUTE MAXIMUM RATINGS Industrial operating temperature……………………………………………………………………………..-40℃ to 85℃ Storage temperature…………………………………………………………………………………………-50℃ to 125℃ Input voltage on any pin relative to ground…………………………………………………………..-0.3V to VCC + 0.3V Maximum voltage…………………………………………………………………………………………………………..8V ESD protection on all pins…………………………………………………………………………………………...>2000V * Stresses exceed those listed under “Absolute Maximum Rating” may cause permanent damage to the device. Functional operation of the device at conditions beyond those listed in the specification is not guaranteed. Prolonged exposure to extreme conditions may affect device reliability or functionality. © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page2 Fremont Micro Devices FT24C16A-Exx Block Diagram Figure 2: Block Diagram © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page3 Fremont Micro Devices FT24C16A-Exx PIN DESCRIPTIONS (A) SERIAL CLOCK (SCL) The rising edge of this SCL input is to latch data into the EEPROM device while the falling edge of this clock is to clock data out of the EEPROM device. (B) SERIAL DATA LINE (SDA) SDA data line is a bi-directional signal for the serial devices. It is an open drain output signal and can be wiredOR with other open-drain output devices. (C) WRITE PROTECT (WP) The FT24C16A devices have a WP pin to protect the whole EEPROM array from programming. Programming operations are allowed if WP pin is left un-connected or input to VIL. Conversely all programming functions are disabled if WP pin is connected to VIH or VCC. Read operations is not affected by the WP pin’s input level. If left unconnected, it is internally recognized as VIL. However, due to capacitive coupling that may appear in customer applications, FMD recommends always connecting the WP pin to a known state. When using a pull-up or pulldown resistor, FMD recommends using 10kΩ or less. MEMORY ORGANIZATION The FT24C16A devices have 128 pages. Since each page has 16 bytes, random word addressing to FT24C16A will require 11 bits data word addresses. DEVICE OPERATION (A) SERIAL CLOCK AND DATA TRANSITIONS The SDA pin is typically pulled to high by an external resistor. Data is allowed to change only when Serial clock SCL is at VIL. Any SDA signal transition may interpret as either a START or STOP condition as described below. (B) START CONDITION With SCL ≥ VIH, a SDA transition from high to low is interpreted as a START condition. All valid commands must begin with a START condition. (C) STOP CONDITION With SCL ≥ VIH, a SDA transition from low to high is interpreted as a STOP condition. All valid read or write commands end with a STOP condition. The device goes into the STANDBY mode if it is after a read command. A STOP condition after page or byte write command will trigger the chip into the STANDBY mode after the selftimed internal programming finish. (D) ACKNOWLEDGE The 2-wire protocol transmits address and data to and from the EEPROM in 8 bit words. The EEPROM acknowledges the data or address by outputting a "0" after receiving each word. The ACKNOWLEDGE signal occurs on the 9th serial clock after each word. © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page4 Fremont Micro Devices FT24C16A-Exx (E) STANDBY MODE The EEPROM goes into low power STANDBY mode after a fresh power up, after receiving a STOP bit in read mode, or after completing a self-time internal programming operation. (F) SOFT RESET After an interruption in protocol power loss or system reset, any two-wire part can be reset by following these steps: 1. Creat a START condition, 2. Clock eighteen data bits “1”, 3. Creat a start condition as SDA is high. SCL SDA START Condition Data Valid Data Transition STOP Condition Figure 3: Timing diagram for START and STOP conditions START Condition SCL Data in Data out ACK Figure 4: Timing diagram for output ACKNOWLEDGE © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page5 Fremont Micro Devices FT24C16A-Exx DEVICE ADDRESSING The 2-wire serial bus protocol mandates an 8 bits device address word after a START bit condition to invoke valid read or write command. The first four most significant bits of the device address must be 1010, which is common to all serial EEPROM devices. The next bit is device address bit. This device address bit (5th) is to match with the external chip select/address pin states. If a match is made, the EEPROM device outputs an ACKNOWLEDGE signal after the 8th read/write bit, otherwise the chip will go into STANDBY mode. The last or 8th bit is a read/write command bit. If the 8th bit is at VIH then the chip goes into read mode. If a “0” is detected, the device enters programming mode. FT24C16A does not use any device address bit. Only one FT24C16A device can be used on the on 2-wire bus. WRITE OPERATIONS (A) BYTE WRITE A byte write operation starts when a micro-controller sends a START bit condition, follows by a proper EEPROM device address and then a write command. EEPROM device will acknowledge at the 9th If the device address bits match the chip select address, the clock cycle. The micro-controller will then send the rest of the lower 8 bits word address. At the 18th cycle, the EEPROM will acknowledge the 8-bit address word. The microcontroller will then transmit the 8 bit data. Following an ACKNOWLDEGE signal from the EEPROM at the 27th clock cycle, the micro-controller will issue a STOP bit. After receiving the STOP bit, the EEPROM will go into a self-timed programming mode during which all external inputs will be disabled. After a programming time of TWC, the byte programming will finish and the EEPROM device will return to the STANDBY mode. (B) PAGE WRITE A page write is similar to a byte write with the exception that one to sixteen bytes can be programmed along the same page or memory row. All FT24C16A are organized to have 16 bytes per memory row or page. With the same write command as the byte write, the micro-controller does not issue a STOP bit after sending the 1st byte data and receiving the ACKNOWLEDGE signal from the EEPROM on the 27th clock cycle. Instead it sends out a second 8-bit data word, with the EEPROM acknowledging at the 36th cycle. This data sending and EEPROM acknowledging cycle repeats until the micro-controller sends a STOP bit after the n × 9th clock cycle. After which the EEPROM device will go into a self-timed partial or full page programming mode. After the page programming completes after a time of TWC, the devices will return to the STANDBY mode. The least significant 4 bits of the word address (column address) increments internally by one after receiving each data word. The rest of the word address bits (row address) do not change internally, but pointing to a specific memory row or page to be programmed. The first page write data word can be of any column address. Up to 16 data words can be loaded into a page. If more then 16 data words are loaded, the 17th data word will be loaded to the 1st data word column address. The 18th data word will be loaded to the 2nd data word column address and so on. In other word, data word address (column address) will “roll” over the previously loaded data. (C) ACKNOWLEDGE POLLING ACKNOWLEDGE polling may be used to poll the programming status during a self-timed internal programming. By issuing a valid read or write address command, the EEPROM will not acknowledge at the 9th clock cycle if the device is still in the self-timed programming mode. However, if the programming completes and the chip has © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page6 Fremont Micro Devices FT24C16A-Exx returned to the STANDBY mode, the device will return a valid ACKNOWLEDGE signal at the 9th clock cycle. READ OPERATIONS The read command is similar to the write command except the 8th read/write bit in address word is set to “1”. The three read operation modes are described as follows: (A) CURRENT ADDRESS READ The EEPROM internal address word counter maintains the last read or write address plus one if the power supply to the device has not been cut off. To initiate a current address read operation, the micro-controller issues a START bit and a valid device address word with the read/write bit (8th) set to “1”. The EEPROM will response with an ACKNOWLEDGE signal on the 9th serial clock cycle. An 8-bit data word will then be serially clocked out. The internal address word counter will then automatically increase by one. For current address read the micro-controller will not issue an ACKNOWLEDGE signal on the 18th clock cycle. The micro-controller issues a valid STOP bit after the 18th clock cycle to terminate the read operation. The device then returns to STANDBY mode. (B) SEQUENTIAL READ The sequential read is very similar to current address read. The micro-controller issues a START bit and a valid device address word with read/write bit (8th) set to “1”. The EEPROM will response with an ACKNOWLEDGE signal on the 9th serial clock cycle. An 8-bit data word will then be serially clocked out. Meanwhile the internally address word counter will then automatically increase by one. Unlike current address read, the micro-controller sends an ACKNOWLEDGE signal on the 18th clock cycle signaling the EEPROM device that it wants another byte of data. Upon receiving the ACKNOWLEDGE signal, the EEPROM will serially clocked out an 8-bit data word based on the incremented internal address counter. If the micro-controller needs another data, it sends out an ACKNOWLEDGE signal on the 27th clock cycle. Another 8-bit data word will then be serially clocked out. This sequential read continues as long as the micro-controller sends an ACKNOWLEDGE signal after receiving a new data word. When the internal address counter reaches its maximum valid address, it rolls over to the beginning of the memory array address. Similar to current address read, the micro-controller can terminate the sequential read by not acknowledging the last data word received, but sending a STOP bit afterwards instead. (C) RANDOM READ Random read is a two-steps process. The first step is to initialize the internal address counter with a target read address using a “dummy write” instruction. The second step is a current address read. To initialize the internal address counter with a target read address, the micro-controller issues a START bit first, follows by a valid device address with the read/write bit (8th) set to “0”. The EEPROM will then acknowledge. The micro-controller will then send the address word. Again the EEPROM will acknowledge. Instead of sending a valid written data to the EEPROM, the micro-controller performs a current address read instruction to read the data. Note that once a START bit is issued, the EEPROM will reset the internal programming process and continue to execute the new instruction - which is to read the current address. © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page7 Fremont Micro Devices FT24C16A-Exx Figure 5: Byte Write Figure 6: Page Write Figure 7: Current Address Read Figure 8: Sequential Read © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page8 Fremont Micro Devices FT24C16A-Exx Figure 9: Random Read Figure 10: SCL and SDA Bus Timing © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page9 Fremont Micro Devices FT24C16A-Exx Electrical Specifications (A)Power-Up Requirements During a power-up sequence, the VCC supplied to the device should monotonically rise from GND to the minimum VCC level, with a slew rate no faster than 0.05 V/μs and no slower then 0.1 V/ms. A decoupling cap should be connected to the VCC PAD which is no smaller than 10nF. (B)Device Reset To prevent inadvertent write operations or any other spurious events from occurring during a power-up sequence, this device includes a Power-on Reset (POR) circuit. Upon power-up, the device will not respond to any commands until the VCC level crosses the internal voltage threshold (VPOR) that brings the device out of Reset and into Standby mode. The system designer must ensure the instructions are not sent to the device until the VCC supply has reached a stable value greater than or equal to the minimum VCC level. Figure 11: Power on and Power down If an event occurs in the system where the VCC level supplied to the device drops below the maximum VPOR level specified, it is recommended that a full power cycle sequence be performed by first driving the VCC pin to GND, waiting at least the minimum tPOFF time and then performing a new power-up sequence in compliance with the requirements defined in this section. © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page10 Fremont Micro Devices FT24C16A-Exx AC CHARACTERISTICS Symbol fSCL tLOW tHIGH tI tAA 1.8 V Parameter Min Clock frequency, SCL tHD.STA tSU.STA tHD.DAT tSU.DAT tR tF tSU.STO tDH tPWR,R(1) tPUP(1) Max Min 400 Clock pulse width low 1.3 Clock pulse width high 0.6 Noise suppression time(1) tBUF 2.5V - 5.5V 1000 0.2 START set-up time Data in hold time Data in set-up time kHz 0.4 µs 0.4 50 Clock low to data out valid Time the bus must be free before a new transmission can start(1) START hold time Unit Max 0.9 0.2 50 µs ns 0.55 µs 1.3 0.5 µs 0.6 0.25 µs 0.6 0.25 µs 0 0 µs 100 100 ns Input rise time(1) 0.3 0.3 µs Input fall time 300 100 ns (1) STOP set-up time 0.6 0.25 µs Date out hold time 50 50 ns 0.1 tWR Vcc slew rate at power up Time required after VCC is stable before the device can accept commands Minimum time at Vcc=0V between power cycles Write cycle time Endurance(1) 25oC, Page Mode, 3.3V tPOFF(1) Notes: 50 0.1 50 V/ms 100 100 µs 500 500 ms 5 1,000,000 5 ms Write Cycles 1. This Parameter is expected by characterization but is not fully screened by test. 2. AC Measurement conditions: RL (Connects to Vcc): 1.3KΩ Input Pulse Voltages: 0.3Vcc to 0.7Vcc Input and output timing reference Voltages: 0.5Vcc © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page11 Fremont Micro Devices FT24C16A-Exx DC CHARACTERISTICS Symbol Parameter Test Conditions Min Typical 1.8 Max Unit s 5.5 V VCC1 Power supply VCC ICC1 Supply read current VCC @ 5.0V SCL = 400 kHz 0.5 1.0 mA ICC2 Supply write current VCC @ 5.0V SCL = 400 kHz 2.0 3.0 mA ISB1 Supply current VCC @ 1.8V, VIN = VCC or VSS < 1.0 µA ISB2 Supply current VCC @ 2.5V, VIN = VCC or VSS < 1.0 µA ISB3 Supply current VCC @ 5.0V, VIN = VCC or VSS < 1.0 µA IIL Input leakage current VIN = VCC or VSS 3.0 µA ILO Output leakage current VIN = VCC or VSS 3.0 µA VIL Input low level -0.6 VCC × 0.3 V VIH Input high level VCC × 0.7 VCC + 0.5 V VOL1 Output low level VCC @ 1.8V, IOL = 0.15 mA 0.2 V VOL2 Output low level VCC @ 3.0V, IOL = 2.1 mA 0.4 V ORDER CODE: FT24C16A - X X X - X Packaging B: Tube T: Tape and Reel Circuit Type HSF R: RoHS G: RoHS and Halogen Free Temp. Range E: -40℃-85℃ Package D: DIP8 S: SOP8 M: MSOP8 T: TSSOP8 L: SOT23-5 P: TSOT23-5 N: DFN8 © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page12 Fremont Micro Devices FT24C16A-Exx ORDER INFORMATION Package Temperature Range Vcc DIP8 -40-85℃ 1.8V-5.5V HSF Packaging Order code RoHS Tube FT24C16A-EDR-B Green Tube FT24C16A-EDG-B Tube FT24C16A-ESR-B Tape and Reel FT24C16A-ESR-T Tube FT24C16A-ESG-B Tape and Reel FT24C16A-ESG-T Tube FT24C16A-EMR-B Tape and Reel FT24C16A-EMR-T Tube FT24C16A-EMG-B Tape and Reel FT24C16A-EMG-T Tube FT24C16A-ETR-B Tape and Reel FT24C16A-ETR-T Tube FT24C16A-ETG-B Tape and Reel FT24C16A-ETG-T RoHS Tape and Reel FT24C16A-ENR-T Green Tape and Reel FT24C16A-ENG-T RoHS Tape and Reel FT24C16A-ELR-T Green Tape and Reel FT24C16A-ELG-T RoHS Tape and Reel FT24C16A-EPR-T Green Tape and Reel FT24C16A-EPG-T RoHS SOP8 -40-85℃ 1.8V-5.5V Green RoHS MSOP8 -40-85℃ 1.8V-5.5V Green RoHS TSSOP8 -40-85℃ 1.8V-5.5V Green DFN8 -40-85℃ 1.8V-5.5V SOT23-5 -40-85℃ 1.8V-5.5V TSOT23-5 -40-85℃ 1.8V-5.5V © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page13 Fremont Micro Devices FT24C16A-Exx DIP8 PACKAGE OUTLINE DIMENSIONS Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max 4.310 0.146 0.170 A 3.710 A1 0.510 A2 3.200 B B1 0.380 0.570 1.524（BSC） 0.015 0.022 0.060（BSC） C 0.204 0.360 0.008 0.014 D 9.000 9.400 0.354 0.370 E 6.200 6.600 0.244 0.260 E1 7.320 7.920 0.288 0.312 0.100（BSC） e 0.020 3.600 2.540 (BSC) 0.126 0.142 L 3.000 3.600 0.118 0.142 E2 8.400 9.000 0.331 0.354 © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page14 Fremont Micro Devices FT24C16A-Exx TSSOP8 PACKAGE OUTLINE DIMENSIONS Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max D 2.900 3.100 0.114 0.122 E 4.300 4.500 0.169 0.177 b 0.190 0.300 0.007 0.012 c 0.090 0.200 0.004 0.008 E1 6.250 6.550 0.246 0.258 A 1.100 0.043 A2 0.800 1.000 0.031 0.039 A1 0.020 0.150 0.001 0.006 e L 0.65 (BSC) 0.500 H θ 0.026 (BSC) 0.700 0.020 0.25 (TYP) 1° © 2019 Fremont Micro Devices Inc. 0.028 0.01 (TYP) 7° 1° Confidential Rev1.4 7° DS24C16A-Exx-page15 Fremont Micro Devices FT24C16A-Exx SOP8 PACKAGE OUTLINE DIMENSIONS Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 1.350 1.750 0.053 0.069 A1 0.100 0.250 0.004 0.010 A2 1.350 1.550 0.053 0.061 b 0.330 0.510 0.013 0.020 c 0.170 0.250 0.006 0.010 D 4.700 5.100 0.185 0.200 E 3.800 4.000 0.150 0.157 E1 5.800 6.200 0.228 0.244 e 1.270 (BSC) 0.050 (BSC) L 0.400 1.270 0.016 0.050 θ 0° 8° 0° 8° © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page16 Fremont Micro Devices FT24C16A-Exx MSOP8 PACKAGE OUTLINE DIMENSIONS Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 0.820 1.100 0.320 0.043 A1 0.020 0.150 0.001 0.006 A2 0.750 0.950 0.030 0.037 b 0.250 0.380 0.010 0.015 c 0.090 0.230 0.004 0.009 D 2.900 3.100 0.114 0.122 e 0.65 (BSC) 0.026 (BSC) E 2.900 3.100 0.114 0.122 E1 4.750 5.050 0.187 0.199 L 0.400 0.800 0.016 0.031 θ 0° 6° 0° 6° © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page17 Fremont Micro Devices FT24C16A-Exx DFN8 PACKAGE OUTLINE DIMENSIONS Symbol Min A 0.70 A1 - b 0.18 c 0.18 D 1.90 Dimensions In Millimeters Nom 0.75 0.02 0.25 0.20 2.00 D2 1.50REF e 0.50BSC Nd E Max 0.80 0.05 0.30 0.25 2.10 1.50BSC 2.90 3.00 3.10 L 0.30 1.60REF 0.40 0.50 h 0.20 E2 L/F Surface Electroplate Dimension（mil） © 2019 Fremont Micro Devices Inc. 0.25 0.30 NIPdAu (Nickel, Pd, Metal) 67*75 Confidential Rev1.4 DS24C16A-Exx-page18 Fremont Micro Devices FT24C16A-Exx SOT-23-5 PACKAGE OUTLINE DIMENSIONS Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 1.050 1.250 0.041 0.049 A1 0.000 0.100 0.000 0.004 A2 1.050 1.150 0.041 0.045 b 0.300 0.500 0.012 0.020 c 0.100 0.200 0.004 0.008 D 2.820 3.020 0.111 0.119 E 1.500 1.700 0.059 0.067 E1 2.650 2.950 0.104 0.116 e 0.95 (BSC) 0.037 (BSC) e1 1.800 2.000 0.071 0.079 L 0.300 0.600 0.012 0.024 0° 8° 0° 6°  © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page19 Fremont Micro Devices FT24C16A-Exx TSOT-23-5 PACKAGE OUTLINE DIMENSIONS Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 0.700 0.900 0.028 0.035 A1 0.000 0.100 0.000 0.004 A2 0.700 0.800 0.028 0.031 b 0.350 0.500 0.014 0.020 c 0.080 0.200 0.003 0.008 D 2.820 3.020 0.111 0.119 E 1.600 1.700 0.063 0.067 E1 2.650 2.950 0.104 0.116 e 0.95 (BSC) 0.037 (BSC) e1 1.90 (BSC) 0.075 (BSC) L  0.300 0.600 0.012 0.024 0° 8° 0° 8° © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page20 Fremont Micro Devices FT24C16A-Exx Fremont Micro Devices (SZ) Limited #5-8, 10/F, Changhong Building, Ke-Ji Nan 12 Road, Nanshan District, Shenzhen Tel: (86 755) 86117811 Fax: (86 755) 86117810 Fremont Micro Devices (Hong Kong) Limited #16, 16/F, Blk B, Veristrong Industrial Centre, 34-36 Au Pui Wan Street, Fotan, Shatin, Hong Kong Tel: (852) 27811186 Fax: (852) 27811144 Web Site: http://www.fremontmicro.com/ * Information furnished is believed to be accurate and reliable. However, Fremont Micro Devices, Incorporated (BVI) assumes no responsibility for the consequences of use of such information or for any infringement of patents of other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent rights of Fremont Micro Devices, Incorporated (BVI). Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. Fremont Micro Devices, Incorporated (BVI) products are not authorized for use as critical components in life support devices or systems without express written approval of Fremont Micro Devices, Incorporated (BVI). The FMD logo is a registered trademark of Fremont Micro Devices, Incorporated (BVI). All other names are the property of their respective owners. © 2019 Fremont Micro Devices Inc. Confidential Rev1.4 DS24C16A-Exx-page21