DS2506
SILICON LABEL DESCRIPTION
The DS2506 64 kbits Add-Only Memory identifies and stores relevant information about the product to
which it is associated. This lot or product specific information can be accessed with minimal interface, for
example a single port pin of a microcontroller. The DS2506 consists of a factory-lasered registration
number that includes a unique 48-bit serial number, an 8-bit CRC, and an 8-bit Family Code (0FH) plus
64 kbits of user-programmable EPROM. The power to program and read the DS2506 is derived entirely
from the 1-Wire communication line. Data is transferred serially via the 1-Wire protocol which requires
only a single data lead and a ground return. The entire device can be programmed and then write-
protected if desired. Alternatively, the part may be programmed multiple times with new data being
appended to, but not overwriting, existing data with each subsequent programming of the device. Note:
Individual bits can be changed only from a logical 1 to a logical 0, never from a logical 0 to a logical 1. A
provision is also included for indicating that a certain page or pages of data are no longer valid and have
been replaced with new or updated data that is now residing at an alternate page address. This page
address redirection allows software to patch data and enhance the flexibility of the device as a stand-alone
database. The 48-bit serial number that is factory-lasered into each DS2506 provides a guaranteed unique
identity which allows for absolute traceability. The PR35 and SOIC packages provide a compact
enclosure that allows standard assembly equipment to handle the device easily for attachment to printed
circuit boards or wiring. Typical applications include storage of calibration constants, maintenance
records, asset tracking, product revision status and access codes.
OVERVIEW
The block diagram in Figure 1 shows the relationships between the major control and memory sections of
the DS2506. The DS2506 has three main data components: 1) 64-bit lasered ROM, 2) 65536-bits
EPROM Data Memory, and 3) 2816-bits EPROM Status Memory. The device derives its power for read
operations entirely from the 1-Wire communication line by storing energy on an internal capacitor during
periods of time when the signal line is high and continues to operate off of this “parasite” power source
during the low times of the 1-Wire line until it returns high to replenish the parasite (capacitor) supply.
During programming, 1-Wire communication occurs at normal voltage levels and then is pulsed
momentarily to the programming voltage to cause the selected EPROM bits to be programmed. The
1-Wire line must be able to provide 12 volts and 10 milliamperes to adequately program the EPROM
portions of the part. Whenever programming voltages are present on the 1-Wire line a special high
voltage detect circuit within the DS2506 generates an internal logic signal to indicate this condition. The
hierarchical structure of the 1-Wire protocol is shown in Figure 2. The bus master must first provide one
of the six ROM Function Commands, 1) Read ROM, 2) Match ROM, 3) Search ROM, 4) Skip ROM, 5)
Overdrive-Skip ROM or 6) Overdrive-Match ROM. Upon completion of an Overdrive ROM command
byte executed at regular speed, the device will enter the Overdrive mode where all subsequent
communication occurs at a higher speed. These commands operate on the 64-bit lasered ROM portion of
each device and can singulate a specific device if many are present on the 1-Wire line as well as indicate
to the bus master how many and what types of devices are present. The protocol required for these ROM
Function Commands is described in Figure 8. After a ROM Function Command is successfully executed,
the memory functions that operate on the EPROM portions of the DS2506 become accessible and the bus
master may issue any one of the five Memory Function Commands specific to the DS2506 to read or
program the various data fields. The protocol for these Memory Function Commands is described in
Figure 5. All data is read and written least significant bit first.
64-BIT LASERED ROM
Each DS2506 contains a unique ROM code that is 64 bits long. The first 8 bits are a 1-Wire family code.
The next 48 bits are a unique serial number. The last 8 bits are a CRC of the first 56 bits. (See Figure 3).
The 64-bit ROM and ROM Function Control section allow the DS2506 to operate as a 1-Wire device and
2 of 25
DALLAS [ DALLAS SEMICONDUCTOR ]
