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DS2480B Schematic ( PDF Datasheet ) - Dallas Semiconductor

Teilenummer DS2480B
Beschreibung Serial 1-Wire Line Driver
Hersteller Dallas Semiconductor
Logo Dallas Semiconductor Logo 




Gesamt 30 Seiten
DS2480B Datasheet, Funktion
www.DataSheet4U.com
www.dalsemi.com
DS2480B
Serial 1-WireTM Line
Driver with Load Sensor
FEATURES
§ Universal, common-ground serial port to 1-
Wireline driver for MicroLAN 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 pullup for crypto iButton, sensors and
EEPROM
§ Load sensor to terminate the stiff pullup as
the energy demand of the crypto iButton
drops
§ Self-calibrating time base with ±5%
tolerance for serial and 1-Wire
communication
§ Slew rate controlled 1-Wire pulldown and
active pullup 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 with 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
PIN ASSIGNMENT
GND
1
8 RXD
1-W 2
NC 3
7 TXD
6 POL
VDD
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 5.5 Volts
VPP - Optional EPROM
Programming Voltage
POL - RXD/TXD Polarity Select
TXD
- Serial Data from UART
RXD
- Serial Data to UART
ORDERING INFORMATION
DS2480BS 8-pin SOIC
Note: The DS2480B will replace the DS2480
later in 1999. It is fully backward compatible to
software drivers that accept a 0 as well as a 1 for
bit 2 of the Reset-command response byte (see
page 7, Table 2)
DESCRIPTION
The DS2480B is a serial port to 1-Wire interface chip that supports regular and Overdrive speeds. It con-
nects directly to UARTs and 5V RS232 systems. Interfacing to RS232C (± 12V levels) requires a passive
clamping circuit and one 5V to ±12V level translator. Internal timers relieve the host of the burden of
generating the time-critical 1-Wire communication waveforms. In contrast to the DS9097(E) where a full
character must be sent by the host for each 1-Wire time slot, the DS2480B can translate each character
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DS2480B Datasheet, Funktion
www.DataSheet4U.com
DS2480B
In addition to the command codes explained in the subsequent sections the DS2480B 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 DS2480B 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.
Reset
The Reset command must be used to begin all 1–Wire communication. The speed selection included in
the command code immediately takes effect. The response byte includes a code for the reaction on the 1–
Wire bus (bits 0 and 1) and a code for the chip revision (bits 2 to 4). If bit 5 of the response byte reads
‘1,’a programming voltage is present on the VPP pin, indicating that one may try programming EPROM
devices.
Single Bit
The Single Bit command is used to generate a single time slot on the 1–Wire bus at the speed indicated by
bits 2 and 3. The type of the time slot (Write-0 or Write-1) is determined by the logic value of bit 4. A
Read Data time slot is identical to the Write-1 time slot. Bits 0 and 1 of the response byte transmitted by
the DS2480B at the end of the time slot reveal the value found on the 1–Wire bus when reading.
For a time slot without a subsequent strong pull–up, bit 1 of the command must be set to 0. For a time slot
immediately followed by a strong pullup bit 1 must be set to 1. As soon as the strong pullup is over, the
device will send a second response byte, code EFh (read 1) or ECh (read 0), depending on the value
found on the 1–Wire bus when reading. The strong pullup directly following the single bit is used in
conjunction with the crypto iButton.
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DS2480B pdf, datenblatt
www.DataSheet4U.com
CONFIGURATION PARAMETER OVERVIEW Table 3
Configurable at
Parameter Description Par. Code Regular Flexible Overdrive
Pull-Down Slew Rate
001
v
Control
Programming Pulse
010 v v
v
Duration
Strong Pullup Duration
011 v v
v
Write-1 Low Time
100
v
Data Sample Offset and
101
v
Write 0 Recovery Time
Load Sensor Threshold
110 v v
v
RS232 Baud Rate
111 v v
v
DS2480B
Default
Reg./Flex. Overdrive
15 V/µs 15 V/µs
512 µs
512 µs
524 ms
8 µs
3 µs
3 µs
3 mA
9.6k bits/s
524 ms
1 µs
1 µs
3 µs
3 mA
9.6k bits/s
The numbers given for parameter 001 (Pulldown Slew Rate Control) are nominal values. They may vary
to some extent 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."
Parameter 110 (Load Sensor Threshold) has been implemented in order to more efficiently support the
high current demand of the crypto iButton. The load sensor is only active if “dynamic” (value code 110)
for the Strong Pullup Duration (parameter 011) has been selected. The nominal and default value for the
load sensor threshold is 3.0 mA with a tolerance band of -25% to +80%. The sensor threshold should be
left at its default value; changes should only be made to compensate for tolerances. Dynamic duration
should only be used when operating crypto iButtons and not for gang-programming 1-Wire EEPROMs or
measuring temperature with multiple temperature sensors converting simultaneously.
For the parameters 010 (Programming Pulse Duration) and 011 (Strong Pullup 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 pullup) 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 DS2480B 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.
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