DS1996 Maxim, DS1996 Datasheet - Page 12

• Manufacturer Part Number: DS1996
• Description: The DS1996 Memory iButton is a rugged read/write data carrier that acts as a localized database that can be easily accessed with minimal hardware
• Manufacturer: Maxim

DS1996
1-WIRE SIGNALING
The DS1996 requires strict protocols to ensure data integrity. The protocol consists of four types of
signaling on one line: Reset Sequence with Reset Pulse and Presence Pulse, Write 0, Write 1 and Read
Data. All these signals except presence pulse are initiated by the bus master. The DS1996 can
communicate at two different speeds, regular speed and Overdrive speed. If not explicitly set into the
overdrive mode, the DS1996 will communicate at regular speed. While in Overdrive Mode the fast timing
applies to all wave forms.
The initialization sequence required to begin any communication with the DS1996 is shown in Figure 10.
A reset pulse followed by a presence pulse indicates the DS1996 is ready to send or receive data given the
correct ROM command and memory function command. The bus master transmits (TX) a reset pulse
(t
, minimum 480 µs at regular speed, 48 µs at Overdrive speed). The bus master then releases the line
RSTL
and goes into receive mode (RX). The 1-Wire bus is pulled to a high state via the pullup resistor. After
detecting the rising edge on the data contact, the DS1996 waits (t
, 15-60 µs at regular speed, 2-6 µs at
PDH
Overdrive speed) and then transmits the presence pulse (t
, 60-240 µs at regular speed, 8-24 µs at
PDL
Overdrive speed).
A Reset Pulse of 480 µs or longer will exit the Overdrive Mode returning the device to regular speed. If
the DS1996 is in Overdrive Mode and the Reset Pulse is no longer than 80 µs the device will remain in
Overdrive Mode.
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