24LC21 1K 2.5V Dual Mode I2C Serial EEPROM FEATURES PACKAGE TYPES PDIP 1 8 VCC NC 2 7 VCLK NC 3 6 SCL VSS 4 5 SDA NC 1 8 VCC NC 2 7 VCLK NC 3 5 SCL VSS 4 5 SDA SOIC 24LC21 DESCRIPTION The Microchip Technology Inc. 24LC21 is a 128 x 8 bit Electrically Erasable PROM. This device is designed for use in applications requiring storage and serial transmission of configuration and control information. Two modes of operation have been implemented: Transmit Only Mode and Bi-Directional Mode. Upon power-up, the device will be in the Transmit Only Mode, sending a serial bit stream of the entire memory array contents, clocked by the VCLK pin. A valid high to low transition on the SCL pin will cause the device to enter the Bi-Directional Mode, with byte selectable read/write capability of the memory array. The 24LC21 is available in a standard 8-pin PDIP and SOIC package in both commercial and industrial temperature ranges. NC 24LC21 • Single supply with operation down to 2.5V • Completely implements DDC1/DDC2 interface for monitor identification • Low power CMOS technology - 1 mA active current typical - 10 µA standby current typical at 5.5V • 2-wire serial interface bus, I2C compatible • Self-timed write cycle (including auto-erase) • Page-write buffer for up to 8 bytes • 100 kHz (2.5V) and 400 kHz (5V) compatibility • Factory programming (QTP) available • 1,000,000 erase/write cycles guaranteed • Data retention > 200 years • 8-pin PDIP and SOIC package • Available for extended temperature ranges - Commercial (C): 0˚C to +70˚C - Industrial (I): -40˚C to +85˚C BLOCK DIAGRAM VCLK HV GENERATOR I/O CONTROL LOGIC MEMORY CONTROL LOGIC XDEC EEPROM ARRAY PAGE LATCHES SDA SCL YDEC VCC VSS SENSE AMP R/W CONTROL DDC is a trademark of the Video Electronics StandarDs Association. I2C is a trademark of Philips Corporation. 1996 Microchip Technology Inc. DS21095F-page 1 This document was created with FrameMaker 4 0 4 24LC21 1.0 ELECTRICAL CHARACTERISTICS 1.1 Maximum Ratings* TABLE 1-1: VCC...................................................................................7.0V All inputs and outputs w.r.t. VSS ............... -0.6V to VCC +1.0V Storage temperature ..................................... -65˚C to +150˚C Ambient temp. with power applied ................ -65˚C to +125˚C Soldering temperature of leads (10 seconds) ............. +300˚C ESD protection on all pins ..................................................≥ 4 kV *Notice: Stresses above those listed under “Maximum ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operational listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability. TABLE 1-2: PIN FUNCTION TABLE Name Function VSS SDA SCL VCLK VCC NC Ground Serial Address/Data I/O Serial Clock (Bi-Directional Mode) Serial Clock (Transmit-Only Mode) +2.5V to 5.5V Power Supply No Connection DC CHARACTERISTICS VCC = +2.5V to 5.5V Commercial (C): Tamb = 0˚C to +70˚C Industrial (I): Tamb = -40˚C to +85˚C Parameter SCL and SDA pins: High level input voltage Low level input voltage Input levels on VCLK pin: High level input voltage Low level input voltage Hysteresis of Schmitt trigger inputs Low level output voltage Low level output voltage Input leakage current Output leakage current Pin capacitance (all inputs/outputs) Operating current Standby current Symbol Min Max Units VIH VIL .7 VCC — — .3 VCC V V VIH VIL VHYS VOL1 VOL2 ILI ILO CIN, COUT 2.0 — .05 VCC — — -10 -10 — .8 .2 VCC — .4 .6 10 10 10 V V V V V µA µA pF ICC Write ICC Read ICCS — — — — 3 1 30 100 mA mA µA µA Conditions VCC ≥ 2.7V (Note 1) VCC < 2.7V (Note 1) (Note 1) IOL = 3 mA, VCC = 2.5V (Note 1) IOL = 6 mA, VCC = 2.5V VIN = .1V to VCC VOUT = .1V to VCC VCC = 5.0V (Note1), Tamb = 25°C, FCLK = 1 MHz VCC = 5.5V, SCL = 400 kHz VCC = 3.0V, SDA = SCL = VCC VCC = 5.5V, SDA = SCL = VCC (Note 2) Note 1: This parameter is periodically sampled and not 100% tested. 2: VLCK must be grounded. DS21095F-page 2 1996 Microchip Technology Inc. 24LC21 TABLE 1-3: AC CHARACTERISTICS Standard Mode Parameter Symbol Vcc= 4.5 - 5.5V Fast Mode Units Remarks Min Max Min Max Clock frequency FCLK Clock high time THIGH Clock low time TLOW SDA and SCL rise time TR SDA and SCL fall time TF START condition hold time THD:STA — 4000 4700 — — 4000 100 — — 1000 300 — — 600 1300 — — 600 400 — — 300 300 — kHz ns ns ns ns ns START condition setup time Data input hold time Data input setup time STOP condition setup time Output valid from clock Bus free time TSU:STA 4700 — 600 — ns THD:DAT TSU:DAT TSU:STO TAA TBUF 0 250 4000 — 4700 — — — 3500 — 0 100 600 — 1300 — — — 900 — ns ns ns ns ns — 250 250 ns — 50 20 + .1 CB — (Note 2) Time the bus must be free before a new transmission can start (Note 1), CB ≤ 100 pF 50 ns (Note 3) — 10 — 10 ms Byte or Page mode — 4000 4700 — 0 2000 — — 500 — — 600 1300 — 0 1000 — — 500 — ns ns ns ns ns 10M — 10M — cycles Output fall time from VIH TOF min to VIL max Input filter spike suppresTSP sion (SDA and SCL pins) Write cycle time TWR Transmit-Only Mode Parameters Output valid from VCLK TVAA VCLK high time TVHIGH VCLK low time TVLOW Mode transition time TVHZ Transmit-Only power up TVPU time Endurance — (Note 1) (Note 1) After this period the first clock pulse is generated Only relevant for repeated START condition (Note 2) 25°C, Vcc = 5.0V, Block Mode (Note 4) Note 1: Not 100% tested. CB = total capacitance of one bus line in pF. 2: As a transmitter, the device must provide an internal minimum delay time to bridge the undefined region (minimum 300 ns) of the falling edge of SCL to avoid unintended generation of START or STOP conditions. 3: The combined TSP and VHYS specifications are due to new Schmitt trigger inputs which provide improved noise and spike suppression. This eliminates the need for a TI specification for standard operation. 4: This parameter is not tested but guaranteed by characterization. For endurance estimates in a specific application, please consult the Total Endurance Model which can be obtained on our BBS or website. 1996 Microchip Technology Inc. DS21095F-page 3 24LC21 2.0 FUNCTIONAL DESCRIPTION The 24LC21 operates in two modes, the Transmit-Only Mode and the Bi-Directional Mode. There is a separate two wire protocol to support each mode, each having a separate clock input and sharing a common data line (SDA). The device enters the Transmit-Only Mode upon power-up. In this mode, the device transmits data bits on the SDA pin in response to a clock signal on the VCLK pin. The device will remain in this mode until a valid high to low transition is placed on the SCL input. When a valid transition on SCL is recognized, the device will switch into the Bi-Directional Mode. The only way to switch the device back to the Transmit-Only Mode is to remove power from the device. 2.1 Transmit-Only Mode The device will power up in the Transmit-Only Mode. This mode supports a unidirectional two wire protocol for transmission of the contents of the memory array. This device requires that it be initialized prior to valid data being sent in the Transmit-Only Mode (see Initialization Procedure, below). In this mode, data is transmitted on the SDA pin in 8 bit bytes, each followed by a FIGURE 2-1: ninth, null bit (see Figure 2-1). The clock source for the Transmit-Only Mode is provided on the VCLK pin, and a data bit is output on the rising edge on this pin. The eight bits in each byte are transmitted most significant bit first. Each byte within the memory array will be output in sequence. When the last byte in the memory array is transmitted, the output will wrap around to the first location and continue. The Bi-Directional Mode Clock (SCL) pin must be held high for the device to remain in the Transmit-Only Mode. 2.2 Initialization Procedure After VCC has stabilized, the device will be in the Transmit-Only Mode. Nine clock cycles on the VCLK pin must be given to the device for it to perform internal synchronization. During this period, the SDA pin will be in a high impedance state. On the rising edge of the tenth clock cycle, the device will output the first valid data bit which will be the most significant bit of a byte. The device will power up at an indeterminate byte address. (See Figure 2-2). TRANSMIT ONLY MODE SCL TVAA TVAA SDA NULL BIT BIT 1 (LSB) BIT 1 (MSB) BIT 7 VCLK TVHIGH FIGURE 2-2: TVLOW DEVICE INITIALIZATION VCC SCL SDA TVAA HIGH IMPEDANCE FOR 9 CLOCK CYCLES TVAA BIT 8 BIT 7 TVPU VCLK DS21095F-page 4 1 2 8 9 10 11 1996 Microchip Technology Inc. 24LC21 3.0 BI-DIRECTIONAL MODE 3.1 The 24LC21 can be switched into the Bi-Directional Mode (see Figure 3-1) by applying a valid high to low transition on the Bi-Directional Mode Clock (SCL). When the device has been switched into the Bi-Directional Mode, the VCLK input is disregarded, with the exception that a logic high level is required to enable write capability. This mode supports a two wire bi-directional data transmission protocol. In this protocol, a device that sends data on the bus is defined to be the transmitter, and a device that receives data from the bus is defined to be the receiver. The bus must be controlled by a master device that generates the Bi-Directional Mode Clock (SCL), controls access to the bus and generates the START and STOP conditions, while the 24LC21 acts as the slave. Both master and slave can operate as transmitter or receiver, but the master device determines which mode is activated. Bi-Directional Mode Bus Characteristics The following bus protocol has been defined: • Data transfer may be initiated only when the bus is not busy. • During data transfer, the data line must remain stable whenever the clock line is HIGH. Changes in the data line while the clock line is HIGH will be interpreted as a START or STOP condition. Accordingly, the following bus conditions have been defined (see Figure 3-2). 3.1.1 BUS NOT BUSY (A) Both data and clock lines remain HIGH. 3.1.2 START DATA TRANSFER (B) A HIGH to LOW transition of the SDA line while the clock (SCL) is HIGH determines a START condition. All commands must be preceded by a START condition. 3.1.3 STOP DATA TRANSFER (C) A LOW to HIGH transition of the SDA line while the clock (SCL) is HIGH determines a STOP condition. All operations must be ended with a STOP condition. FIGURE 3-1: MODE TRANSITION Transmit Only Mode Bi-Directional Mode SCL TVHZ SDA VCLK FIGURE 3-2: DATA TRANSFER SEQUENCE ON THE SERIAL BUS VHYS SCL THD:STA TSU:STA TSU:STO SDA START 1996 Microchip Technology Inc. STOP DS21095F-page 5 24LC21 3.1.4 3.1.5 DATA VALID (D) Each receiving device, when addressed, is obliged to generate an acknowledge after the reception of each byte. The master device must generate an extra clock pulse which is associated with this acknowledge bit. The state of the data line represents valid data when, after a START condition, the data line is stable for the duration of the HIGH period of the clock signal. The data on the line must be changed during the LOW period of the clock signal. There is one clock pulse per bit of data. Note: Each data transfer is initiated with a START condition and terminated with a STOP condition. The number of the data bytes transferred between the START and STOP conditions is determined by the master device and is theoretically unlimited, although only the last eight will be stored when doing a write operation. When an overwrite does occur it will replace data in a first in first out fashion. FIGURE 3-3: ACKNOWLEDGE The 24LC21 does not generate any acknowledge bits if an internal programming cycle is in progress. The device that acknowledges has to pull down the SDA line during the acknowledge clock pulse in such a way that the SDA line is stable LOW during the HIGH period of the acknowledge related clock pulse. Of course, setup and hold times must be taken into account. A master must signal an end of data to the slave by not generating an acknowledge bit on the last byte that has been clocked out of the slave. In this case, the slave must leave the data line HIGH to enable the master to generate the STOP condition. BUS TIMING START/STOP VHYS SCL THD:STA TSU:STA TSU:STO SDA START FIGURE 3-4: STOP BUS TIMING DATA TR TF THIGH TLOW SCL TSU:STA THD:DAT TSU:DAT TSU:STO THD:STA SDA IN TSP TAA THD:STA TAA TBUF SDA OUT DS21095F-page 6 1996 Microchip Technology Inc. 24LC21 3.1.6 SLAVE ADDRESS After generating a START condition, the bus master transmits the slave address consisting of a 7-bit device code (1010) for the 24LC21, followed by three don’t care bits. The eighth bit of slave address determines if the master device wants to read or write to the 24LC21 (see Figure 3-5). The 24LC21 monitors the bus for its corresponding slave address all the time. It generates an acknowledge bit if the slave address was true and it is not in a programming mode. Operation Control Code Chip Select R/W Read Write 1010 1010 XXX XXX 1 0 FIGURE 3-5: CONTROL BYTE ALLOCATION START READ/WRITE SLAVE ADDRESS R/W A 4.0 WRITE OPERATION 4.1 Byte Write Following the start signal from the master, the slave address (4 bits), the don’t care bits (3 bits) and the R/W bit which is a logic low is placed onto the bus by the master transmitter. This indicates to the addressed slave receiver that a byte with a word address will follow after it has generated an acknowledge bit during the ninth clock cycle. Therefore, the next byte transmitted by the master is the word address and will be written into the address pointer of the 24LC21. After receiving another acknowledge signal from the 24LC21 the master device will transmit the data word to be written into the addressed memory location. The 24LC21 acknowledges again and the master generates a stop condition. This initiates the internal write cycle, and during this time the 24LC21 will not generate acknowledge signals (see Figure 4-1). It is required that VCLK be held at a logic high level in order to program the device. This applies to byte write and page write operation. Note that VCLK can go low while the device is in its self-timed program operation and not affect programming. 4.2 1 0 1 0 X X Page Write The write control byte, word address and the first data byte are transmitted to the 24LC21 in the same way as in a byte write. But instead of generating a stop condition the master transmits up to eight data bytes to the 24LC21 which are temporarily stored in the on-chip page buffer and will be written into the memory after the master has transmitted a stop condition. After the receipt of each word, the three lower order address pointer bits are internally incremented by one. The higher order five bits of the word address remains constant. If the master should transmit more than eight words prior to generating the stop condition, the address counter will roll over and the previously received data will be overwritten. As with the byte write operation, once the stop condition is received an internal write cycle will begin (see Figure 4-2). X It is required that VCLK be held at a logic high level in order to program the device. This applies to byte write and page write operation. Note that VCLK can go low while the device is in its self-timed program operation and not affect programming. FIGURE 4-1: BYTE WRITE BUS ACTIVITY MASTER S T A R T SDA LINE S CONTROL BYTE BUS ACTIVITY WORD ADDRESS S T O P DATA P A C K A C K A C K VCLK 1996 Microchip Technology Inc. DS21095F-page 7 24LC21 FIGURE 4-2: PAGE WRITE BUS ACTIVITY MASTER S T A R T SDA LINE S BUS ACTIVITY CONTROL BYTE WORD ADDRESS (n) DATA n S T O P DATA n + 15 DATA n + 1 P A C K A C K A C K A C K A C K VCLK 5.0 ACKNOWLEDGE POLLING FIGURE 5-1: Since the device will not acknowledge during a write cycle, this can be used to determine when the cycle is complete (this feature can be used to maximize bus throughput). Once the stop condition for a write command has been issued from the master, the device initiates the internally timed write cycle. ACK polling can be initiated immediately. This involves the master sending a start condition followed by the control byte for a write command (R/W = 0). If the device is still busy with the write cycle, then no ACK will be returned. If the cycle is complete, then the device will return the ACK and the master can then proceed with the next read or write command. See Figure 5-1 for the flow diagram. ACKNOWLEDGE POLLING FLOW Send Write Command Send Stop Condition to Initiate Write Cycle Send Start Send Control Byte with R/W = 0 Did Device Acknowledge (ACK = 0)? NO YES Next Operation 6.0 WRITE PROTECTION When using the 24LC21 in the Bi-Directional Mode, the VCLK pin operates as the write protect control pin. Setting VCLK high allows normal write operations, while setting VCLK low prevents writing to any location in the array. Connecting the VCLK pin to VSS would allow the 24LC21 to operate as a serial ROM, although this configuration would prevent using the device in the Transmit-Only Mode. DS21095F-page 8 1996 Microchip Technology Inc. 24LC21 7.0 READ OPERATION Read operations are initiated in the same way as write operations with the exception that the R/W bit of the slave address is set to one. There are three basic types of read operations: current address read, random read and sequential read. 7.1 7.3 Current Address Read The 24LC21 contains an address counter that maintains the address of the last word accessed, internally incremented by one. Therefore, if the previous access (either a read or write operation) was to address n, the next current address read operation would access data from address n + 1. Upon receipt of the slave address with R/W bit set to one, the 24LC21 issues an acknowledge and transmits the eight bit data word. The master will not acknowledge the transfer but does generate a stop condition and the 24LC21 discontinues transmission (Figure 7-1). 7.2 Random read operations allow the master to access any memory location in a random manner. To perform this type of read operation, first the word address must be set. This is done by sending the word address to the 24LC21 as part of a write operation. After the word address is sent, the master generates a start condition following the acknowledge. This terminates the write operation, but not before the internal address pointer is To provide sequential reads the 24LC21 contains an internal address pointer which is incremented by one at the completion of each operation. This address pointer allows the entire memory contents to be serially read during one operation. Noise Protection The 24LC21 employs a VCC threshold detector circuit which disables the internal erase/write logic if the VCC is below 1.5 volts at nominal conditions. The SCL and SDA inputs have Schmitt trigger and filter circuits which suppress noise spikes to assure proper device operation even on a noisy bus. CURRENT ADDRESS READ BUS ACTIVITY MASTER S T A R T SDA LINE S CONTROL BYTE S T O P DATA n P N O A C K BUS ACTIVITY FIGURE 7-2: Sequential Read Sequential reads are initiated in the same way as a random read except that after the 24LC21 transmits the first data byte, the master issues an acknowledge as opposed to a stop condition in a random read. This directs the 24LC21 to transmit the next sequentially addressed 8 bit word (see Figure 7-3). 7.4 Random Read FIGURE 7-1: set. Then the master issues the control byte again but with the R/W bit set to a one. The 24LC21 will then issue an acknowledge and transmits the eight bit data word. The master will not acknowledge the transfer but does generate a stop condition and the 24LC21 discontinues transmission (Figure 7-2). A C K RANDOM READ T S T A R T S S S T BUS ACTIVITY A MASTER R SDA LINE BUS ACTIVITY CONTROL BYTE WORD ADDRESS (n) A C K A C K CONTROL BYTE S T O P DATA n P A C K N O A C K 1996 Microchip Technology Inc. DS21095F-page 9 24LC21 FIGURE 7-3: BUS ACTIVITY MASTER SEQUENTIAL READ CONTROL BYTE DATA n DATA n + 1 DATA n + 2 S T O P DATA n + X P SDA LINE BUS ACTIVITY A C K A C K A C K A C K N O A C K 8.0 PIN DESCRIPTIONS 8.1 SDA This pin is used to transfer addresses and data into and out of the device, when the device is in the Bi-Directional Mode. In the Transmit-Only Mode, which only allows data to be read from the device, data is also transferred on the SDA pin. This pin is an open drain terminal, therefore the SDA bus requires a pullup resistor to VCC (typical 10KΩ for 100 kHz, 1KΩ for 400 kHz). For normal data transfer in the Bi-Directional Mode, SDA is allowed to change only during SCL low. Changes during SCL high are reserved for indicating the START and STOP conditions. 8.2 SCL This pin is the clock input for the Bi-Directional Mode, and is used to synchronize data transfer to and from the device. It is also used as the signaling input to switch the device from the Transmit Only Mode to the Bi-Directional Mode. It must remain high for the chip to continue operation in the Transmit Only Mode. 8.3 VCLK This pin is the clock input for the Transmit Only Mode. In the Transmit Only Mode, each bit is clocked out on the rising edge of this signal. In the Bi-Directional Mode, a high logic level is required on this pin to enable write capability. DS21095F-page 10 1996 Microchip Technology Inc. 24LC21 24LC21 Product Identification System To order or to obtain information, e.g., on pricing or delivery, please use the listed part numbers, and refer to the factory or the listed sales offices. 24LC21 - /P Package: Temperature Range: Device: 1996 Microchip Technology Inc. P = Plastic DIP (300 mil Body), 8-lead SN = Plastic SOIC (150 mil Body), 8-lead Blank = 0˚C to +70˚C I = -40˚C to +85˚C 24LC21 24LC21T Dual Mode I2C Serial EEPROM Dual Mode I2C Serial EEPROM (Tape and Reel) DS21095F-page 11 WORLDWIDE SALES & SERVICE AMERICAS ASIA/PACIFIC EUROPE Corporate Office Microchip Technology Inc. 2355 West Chandler Blvd. Chandler, AZ 85224-6199 Tel: 602 786-7200 Fax: 602 786-7277 Technical Support: 602 786-7627 Web: http://www.microchip.com Atlanta Microchip Technology Inc. 500 Sugar Mill Road, Suite 200B Atlanta, GA 30350 Tel: 770 640-0034 Fax: 770 640-0307 Boston Microchip Technology Inc. 5 Mount Royal Avenue Marlborough, MA 01752 Tel: 508 480-9990 Fax: 508 480-8575 Chicago Microchip Technology Inc. 333 Pierce Road, Suite 180 Itasca, IL 60143 Tel: 708 285-0071 Fax: 708 285-0075 Dallas Microchip Technology Inc. 14651 Dallas Parkway, Suite 816 Dallas, TX 75240-8809 Tel: 972 991-7177 Fax: 972 991-8588 Dayton Microchip Technology Inc. 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Unit 6, The Courtyard Meadow Bank, Furlong Road Bourne End, Buckinghamshire SL8 5AJ Tel: 44 1628 850303 Fax: 44 1628 850178 France Arizona Microchip Technology SARL Zone Industrielle de la Bonde 2 Rue du Buisson aux Fraises 91300 Massy - France Tel: 33 1 69 53 63 20 Fax: 33 1 69 30 90 79 Germany Arizona Microchip Technology GmbH Gustav-Heinemann-Ring 125 D-81739 Muenchen, Germany Tel: 49 89 627 144 0 Fax: 49 89 627 144 44 Italy Arizona Microchip Technology SRL Centro Direzionale Colleone Pas Taurus 1 Viale Colleoni 1 20041 Agrate Brianza Milan Italy Tel: 39 39 6899939 Fax: 39 39 689 9883 JAPAN Microchip Technology Intl. Inc. Benex S-1 6F 3-18-20, Shin Yokohama Kohoku-Ku, Yokohama Kanagawa 222 Japan Tel: 81 45 471 6166 Fax: 81 45 471 6122 9/3/96 All rights reserved. 1996, Microchip Technology Incorporated, USA. 9/96 Printed on recycled paper. Information contained in this publication regarding device applications and the like is intended through suggestion only and may be superseded by updates. No representation or warranty is given and no liability is assumed by Microchip Technology Incorporated with respect to the accuracy or use of such information, or infringement of patents or other intellectual property rights arising from such use or otherwise. Use of Microchip’s products as critical components in life support systems is not authorized except with express written approval by Microchip. No licenses are conveyed, implicitly or otherwise, under any intellectual property rights. The Microchip logo and name are registered trademarks of Microchip Technology Inc. All rights reserved. All other trademarks mentioned herein are the property of their respective companies. DS21095F-page 12 1996 Microchip Technology Inc.