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DS2480 Schematic ( PDF Datasheet ) - Dallas Semiconducotr

Teilenummer DS2480
Beschreibung Serial 1-Wire Line Driver
Hersteller Dallas Semiconducotr
Logo Dallas Semiconducotr Logo 




Gesamt 28 Seiten
DS2480 Datasheet, Funktion
www.dalsemi.com
FEATURES
Universal, common-ground serial port to
1-WireTM line driver for MicroLANTM
applications
Works with all iButtons™ and MicroLAN-
compatible 1-Wire slave devices
Communicates at regular and Overdrive 1-Wire
speed and serial port data rates of 9600
(default), 19200, 57600 and 115200 bps
Supports 12V EPROM programming and stiff
5V pull-up for Crypto iButton, sensors and
EEPROM
Self-calibrating time base with ±5% tolerance
for serial and 1-Wire communication
Slew rate controlled 1-Wire pull-down and
active pull-up to accommodate long lines and
reduce radiation
User-selectable RXD/TXD polarity minimizes
component count when interfacing to 5V
based RS232 systems or directly to UARTs
Programmable 1-Wire timing and driver
characteristics accommodate a wide range of
MicroLAN configurations at regular speed
Smart protocol combines data and control
information without requiring extra pins
Compatible to optical, IR and RF to RS232
converters
Low cost 8-pin SOIC surface mount package
Operates over 4.5V to 5.5V from -40°C to
+85°C
DS2480
Serial 1-Wire™ Line Driver
PIN ASSIGNMENT
GND
1-W
NC
VDD
1 8 RXD
2 7 TXD
3 6 POL
4 5 VPP
8-PIN SOIC
(150 MIL)
PIN DESCRIPTION
GND
Ground
1-W 1-Wire Input/Output
NC No Connection
VDD 4.5 to 5.5V
VPP Optional EPROM
Programming Voltage
POL RXD/TXD Polarity Select
TXD
Serial Data from UART
RXD
Serial Data to UART
ORDERING INFORMATION
DS2480S
8-pin SOIC
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DS2480 Datasheet, Funktion
DS2480
While being in the Data Mode the DS2480 checks each byte received from the host for the reserved code
that is used to switch back to Command Mode. To be able to write any possible code (including the
reserved one) to the 1-Wire bus, the transition to the Command Mode is as follows: After having received
the code for switching to Command Mode, the device temporarily enters the Check Mode where it waits
for the next byte. If both bytes are the same, the byte is sent once to the 1-Wire bus and the device returns
to the Data Mode. If the second byte is different from the reserved code, it will be executed as command
and the device finally enters the Command Mode. As a consequence, if the reserved code that normally
switches to Command Mode is to be written to the 1-Wire bus, this code byte must be sent twice
(duplicated). This detail must be considered carefully when developing software drivers for the DS2480.
After having completed a memory function with a device on the 1-Wire bus it is recommended to issue a
Reset Pulse. This means that the DS2480 has to be switched to Command mode. The host then sends the
appropriate command code and continues performing other tasks. If during this time a device arrives at
the 1-Wire bus it will generate a presence pulse. The DS2480 will recognize this unsolicited presence
pulse and notify the host by sending a byte such as XXXXXX01b. The Xs represent undefined bit values.
The fact that the host receives the byte unsolicited together with the pattern 01b in the least significant
two bits marks the bus arrival. If the DS2480 is left in Data Mode after completing a memory function
command it will not report any bus arrival to the host.
COMMAND CODE OVERVIEW
The DS2480 is controlled by a variety of commands. All command codes are 8 bits long. The most
significant bit of each command code distinguishes between communication and configuration
commands. Configuration commands access the configuration registers. They can write or read any of the
configurable parameters. Communication commands use data of the configuration register in order to
generate activity on the 1-Wire bus and/or (dis) arm the strong pull-up after every byte or (de) activate the
Search Accelerator without generating activity on the 1-Wire bus. Details on the command codes are
included in the State Transition diagram (Figure 2). A full explanation is given in the subsequent sections
Communication Commands and Configuration Commands.
In addition to the command codes explained in the subsequent sections the DS2480 understands the
following reserved command codes:
E1h switch to Data Mode
E3h switch to Command Mode
F1h pulse termination
Except for these reserved commands, the Search Accelerator control and the first byte after power-on
reset or master reset cycle, every legal command byte generates a response byte. The pulse termination
code triggers the response byte of the terminated pulse command. Illegal command bytes do not generate
a command response byte.
Once the device is switched back from Data Mode to Command Mode one must not repeat the E3h
command while the Command Mode is still active.
COMMUNICATION COMMANDS
The DS2480 supports four communication function commands: Reset, Single Bit, Pulse, and Search
Accelerator control. Details on the assignment of each bit of the command codes are shown in Table 1.
The corresponding command response bytes are detailed in Table 2. The Reset, Search Accelerator
Control and Single Bit commands include bits to select the 1-Wire communication speed (regular,
flexible regular, Overdrive). Even if a command does not generate activity on the 1-Wire bus, these bits
are latched inside the device and will take effect immediately.
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DS2480 pdf, datenblatt
CONFIGURATION COMMAND OVERVIEW TABLE 3
Parameter Description Par. Code Configurable at
Default
Regular Flexible Overdrive Reg./Flex.
Pull-Down Slew Rate 001
15 V/µs
Control
Programming Pulse
010
512 µs
Duration
Strong Pull-up Duration 011 √ √
524 ms
Write 1 low time
100
8 µs
Data Sample Offset and 101
3 µs
Write 0 Recovery Time
3 µs
RS232 Baud Rate
111 √ √
9.6k bits/s
DS2480
Overdrive
15 V/µs
512 µs
524 ms
1 µs
1 µs
3 µs
9.6k bits/s
The numbers given for parameter 001 (Pull-Down Slew Rate Control) are nominal values. They may vary
as specified in the Electrical Characteristics section and are almost independent of the load on the 1-Wire
bus. Information on how to select the optimum value of this parameter is given in section “Controlled
Edges”.
For the parameters 010 (Programming Pulse Duration) and 011 (Strong Pull-Up Duration) one may select
indefinite duration. This value, however, should only be selected if one is not going to switch the device
to Data Mode. As long as the device stays in Command Mode, any pulse function (programming or
strong pull-up) that uses one of these parameters can be terminated by sending the command code F1h.
Termination is not possible if the device is in Data Mode.
Parameter 111 (RS232 Baud Rate) has two functions. It selects the baud rate and allows inversion of the
signal at the RXD pin. Using one of the value codes 100 to 111 will set the polarity at RXD to the
opposite of what is defined by the logic level at the POL pin (asymmetry bit, see Figure 1). This may
reduce the component count in some applications of the device. Note that when changing the baud rate,
the DS2480 will send the command response byte at the new data rate.
A short explanation on the use of parameters 100 (Write 1 low time) and 101 (Data Sample Offset/Write
0 Recovery Time) is given in the section “Timing Diagrams” later in this document. The parameter code
110 is reserved for future extensions; one should not change the value code from its default setting.
CONFIGURATION PARAMETER VALUE CODES Table 4
Value Codes
Parameter Code
000 001 010 011 100 101
001 (PDSRC)
15 2.2 1.65 1.37 1.1 0.83
010 (PPD)
32 64 128 256 512 1024
011 (SPUD)
16.4 65.5 131 262 524 1048
100 (W1LT)
8 9 10 11 12 13
101 (DSO/W0RT)
345678
111 (RBR)
9.6 19.2 57.6 115.2 9.6 19.2
110
0.7
2048
2096
14
9
57.6
111
0.55
15
10
115.2
Unit
V/µs
µs
ms
µs
µs
kbits/s
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