DS2480 Dallas Semiconducotr, DS2480 Datasheet - Page 3

• Manufacturer Part Number: DS2480
• Description: Serial 1.Wire Line Driver
• Manufacturer: Dallas Semiconducotr

DS2480 BLOCK DIAGRAM Figure 1
DEVICE OPERATION
The DS2480 can be described as a complex state
machine with two static and several dynamic states.
Two device–internal flags as well as functions assigned
to certain bit positions in the command codes determine
the behavior of the chip, as shown in the state transition
diagram (Figure 2). The DS2480 requires and gener-
ates a communication protocol of 8 data bits per charac-
ter, 1 stop bit and no parity. It is permissible to use two
stop bits on the TXD line. However, the DS2480 will only
assert a single stop bit on RXD.
When powering up, the DS2480 performs a master
reset cycle and enters the Command Mode, which is
one of the two static states. The device now expects to
receive one 1–Wire reset command on the TXD line
sent by the host at a data rate of 9600 bits per second
(see section Communication Commands for details).
This command byte is required solely for calibration of
RXD
POL
TXD
CONFIGURATION
PROTOCOL
PROTOCOL
REGISTER
ANALYZER
ANALYZER
MUX
MS BIT OF SPEED CONTROL
(1 = RXD IS INVERTED)
the timing generator the DS2480 and is not translated
into any activity on the 1–Wire bus. After this first com-
mand byte the device is ready to receive and execute
any command as described later in this document.
A master reset cycle can also be generated by means of
software. This may be necessary if the host for any rea-
son has lost synchronization with the device. The
DS2480 will perform a master reset cycle equivalent to
the power–on reset if it detects start polarity in place of
the stop bit. The host has several options to generate
this condition. These include making the UART gener-
ate a break signal, sending a NULL character at a data
rate of 4800 bps and sending any character with parity
enabled and selecting space polarity for the parity bit.
As with the power–on reset, the DS2480 requires a
1–Wire reset command sent by the host at a data rate of
9600 bps for calibration.
GENERATOR
TIMING
CONVERTER
PROTOCOL
1–WIRE
DRIVER
V
PP
042498 3/26
DS2480
1–W