Upgrading Two-Wire Serial EEPROM Memory 1. Introduction As applications are updated, many may require an increase in memory storage in order to account for additional system data. This may require upgrading to a higher density two-wire Serial EEPROM product. The below mentioned Atmel® two-wire Serial EEPROM devices use the same package pin-out, and the same software protocol sequence making upgrading to a higher density product a simple and straightforward process. However, there are a few differences to consider when upgrading to a higher density. • Memory page size • Device / Word Address 2. Memory Page Size The two-wire Serial EEPROM device family is divided into the following by memory page size. Device Part Number Device Density Page Size AT24C01x/ C02x 1K, 2K(low density) 8 byte page AT24C04x/ C08x/ C16x 4K, 8K, 16K (low density) 16 byte page AT24C32x/ C64x 32K, 64K (medium density) 32 byte page AT24C128x/ C256x 128K, 256K (high density) 64 byte page AT24C512x/ AT24C1024x 512K, 1M (high density) 128 byte page Upgrading Two-Wire Serial EEPROM Memory AT24C01x AT24C02x AT24C32x AT24C64x AT24C128x AT24C256x AT24C512x AT24C1024x All Atmel two-wire Serial EEPROM devices support both byte and page mode programming operations. As the page size increases, so does the ability to program more data with a single write operation. For example it requires 4 separate sequential 8 byte write sequences to program 32 consecutive bytes using a 2K device, but would only require one 32 byte sequence to program those same locations using a 32K device. This is a significant time savings considering each write cycle can take up to 5ms, thus reducing programming time by a factor of four. 5237A–SEEPR–4/07 3. Device / Word Address 3.1 Overview Depending on density of device, Atmel two-wire serial communications requires a device address followed by either one or two word address(s) for all write and read commands. The device address will always starts with the two-wire identifier 1010 which establishes communication with the two-wire product family. Following the identifier are the device / page address bits. For the low density family (1K – 16K) only one word address follows the device address. Since an eight bit address field can only access 256 different byte locations (2K bits), the 4K-16K devices make use of page address bits embedded in the device address field. These page address bits are traded off with the Device / Page address pins 1, 2, and 3 thus resulting in the reduced cascadability. The medium and high density device use a two word address therefore, devices 32K – 512K all have 8 device cascadability with only the 1 Meg device needing to use the a single embedded page address bit. The below table (refer to Figure 3-1) is provided for easy reference to determine these device / word address differences and bus cascadability. Figure 3-1. Two-Wire Family Attributes Device Address / Page Byte 3.2 Word Address Bytes Maximum Devices on Bus 1K/2K 1 0 1 0 A2 A1 A0 R/W 1 8 4K 1 0 1 0 A2 A1 P0 R/W 1 4 8K 1 0 1 0 A2 P1 P0 R/W 1 2 16K 1 0 1 0 P2 P1 P0 R/W 1 1 32K-512K 1 0 1 0 A2 A1 A0 R/W 2 8 1M 1 MSB 0 1 0 A2 A1 P0 R/W LSB 2 4 Upgrades within the Low Density Family The low density family (1K – 16K) all use a single word address (refer to Figure 3-2). When upgrading within the low density family the difference in device / page pin configuration needs to be considered along with differences in page size. All other features and commands are the same. 2 AT24C01B/C02B/C04B/C08B/C16B/C32C/C64C/C128B/C256B/C512B/C1024B 5237A–SEEPR–4/07 AT24C01B/C02B/C04B/C08B/C16B/C32C/C64C/C128B/C256B/C512B/C1024B 3.3 Upgrades from Low Density to Medium and High Densities Upgrading from low to medium and high density will require the additional byte of word address (refer to Figure 3-3). Therefore system software will need to be adjusted to compensate for the extra word address. Also any differences in the device / page address bits will need to be considered along with changes in page size. 3.4 Upgrades within and from Medium to High Densities All devices from 32K – 512K will require no system changes and can be interchanged with only the page size differences to consider. Figure 3-2. Low Density Random Read S T A R T W R I T E DEVICE ADDRESS S T A R T WORD ADDRESS n S T O P R E A D DEVICE ADDRESS * SDA LINE M S B L R A S / C BW K M S B L A S C B K M S B L S B DATA n A C K A C K DUMMY WRITE Figure 3-3. N O Medium and High Density Random Read S T A R T DEVICE ADDRESS W R I T E S T A R T 1st, 2nd WORD ADDRESS n DEVICE ADDRESS S T O P R E A D 0 SDA LINE M S B L R A S / C BW K M S B DUMMY WRITE L A S C B K A C K DATA n N O A C K 4. Conclusion Upgrading density within the two wire family is a straightforward process as long as you consider the following possible differences. • Page sizes changes • Device / Page address configuration • One or Two word address byte(s) 3 5237A–SEEPR–4/07 Headquarters Operations Atmel Corporation Memory 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(408) 441-0311 Fax: 1(408) 487-2600 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(408) 441-0311 Fax: 1(408) 436-4314 Microcontrollers International Atmel Asia Room 1219 Chinachem Golden Plaza 77 Mody Road Tsimshatsui East Kowloon Hong Kong Tel: (852) 2721-9778 Fax: (852) 2722-1369 Atmel Europe Le Krebs 8, Rue Jean-Pierre Timbaud BP 309 78054 Saint-Quentin-en-Yvelines Cedex France Tel: (33) 1-30-60-70-00 Fax: (33) 1-30-60-71-11 Atmel Japan 9F, Tonetsu Shinkawa Bldg. 1-24-8 Shinkawa Chuo-ku, Tokyo 104-0033 Japan Tel: (81) 3-3523-3551 Fax: (81) 3-3523-7581 2325 Orchard Parkway San Jose, CA 95131, USA Tel: 1(408) 441-0311 Fax: 1(408) 436-4314 La Chantrerie BP 70602 44306 Nantes Cedex 3 France Tel: (33) 2-40-18-18-18 Fax: (33) 2-40-18-19-60 ASIC/ASSP/Smart Cards Zone Industrielle 13106 Rousset Cedex France Tel: (33) 4-42-53-60-00 Fax: (33) 4-42-53-60-01 RF/Automotive Theresienstrasse 2 Postfach 3535 74025 Heilbronn Germany Tel: (49) 71-31-67-0 Fax: (49) 71-31-67-2340 1150 East Cheyenne Mtn. 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