DS28E01-100+ Maxim Integrated, DS28E01-100+ Datasheet - Page 16

• Manufacturer Part Number: DS28E01-100+
• Description: EEPROM
• Manufacturer: Maxim Integrated

1Kb Protected 1-Wire EEPROM
with SHA-1 Engine
To maximize the data throughput in a multidrop environ-
ment, the Resume command is available. This command
checks the status of the RC bit and, if it is set, directly
transfers control to the memory and SHA-1 function com-
mands, similar to a Skip ROM command. The only way to
set the RC bit is through successfully executing the
Match ROM, Search ROM, or Overdrive-Match ROM
command. Once the RC bit is set, the device can repeat-
edly be accessed through the Resume command.
Accessing another device on the bus clears the RC bit,
preventing two or more devices from simultaneously
responding to the Resume command.
On a single-drop bus this command can save time by
allowing the bus master to access the memory func-
tions without providing the 64-bit registration number.
Unlike the normal Skip ROM command, the Overdrive-
Skip ROM command sets the DS28E01-100 into the
overdrive mode (OD = 1). All communication following
this command must occur at overdrive speed until a
reset pulse of minimum 480µs duration resets all de-
vices on the bus to standard speed (OD = 0).
When issued on a multidrop bus, this command sets all
overdrive-supporting devices into overdrive mode. To
subsequently address a specific overdrive-supporting
device, a reset pulse at overdrive speed must be
issued followed by a Match ROM or Search ROM com-
mand sequence. This speeds up the time for the
search process. If more than one slave supporting
overdrive is present on the bus and the Overdrive-Skip
ROM command is followed by a read command, data
collision occurs on the bus as multiple slaves transmit
simultaneously (open-drain pulldowns produce a wired-
AND result).
The Overdrive-Match ROM command followed by a 64-
bit registration number transmitted at overdrive speed
allows the bus master to address a specific DS28E01-
100 on a multidrop bus and to simultaneously set it in
overdrive mode. Only the DS28E01-100 that exactly
matches the 64-bit number responds to the subsequent
memory or SHA-1 function command. Slaves already in
overdrive mode from a previous Overdrive-Skip ROM or
successful Overdrive-Match ROM command remain in
overdrive mode. All overdrive-capable slaves return to
standard speed at the next reset pulse of minimum
480µs duration. The Overdrive-Match ROM command
can be used with a single device or multiple devices on
the bus.
DS28E01-100
28
Overdrive-Match ROM [69h]
Overdrive-Skip ROM [3Ch]
ABRIDGED DATA SHEET
Resume [A5h]
The DS28E01-100 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-zero, write-one, and read-
data. Except for the presence pulse, the bus master
initiates all falling edges. The DS28E01-100 can com-
municate at two different speeds: standard speed and
overdrive speed. If not explicitly set into the overdrive
mode, the DS28E01-100 communicates at standard
speed. While in overdrive mode, the fast timing applies
to all waveforms.
To get from idle to active, the voltage on the 1-Wire line
needs to fall from V
from active to idle, the voltage needs to rise from
V
voltage to make this rise is seen in Figure 11 as ε, and
its duration depends on the pullup resistor (R
and the capacitance of the 1-Wire network attached.
The voltage V
when determining a logical level, not triggering any
events.
Figure 11 shows the initialization sequence required to
begin any communication with the DS28E01-100. A
reset pulse followed by a presence pulse indicates that
the DS28E01-100 is ready to receive data, given the
correct ROM and memory and SHA-1 function com-
mand. If the bus master uses slew-rate control on the
falling edge, it must pull down the line for t
compensate for the edge. A t
longer exits the overdrive mode, returning the device to
standard speed. If the DS28E01-100 is in overdrive
mode and t
remains in overdrive mode. If the device is in overdrive
mode and t
resets, but the communication speed is undetermined.
After the bus master has released the line it goes into
receive mode. Now the 1-Wire bus is pulled to V
through the pullup resistor or, in the case of a DS2482-
x00 or DS2480B driver, through active circuitry. When
the threshold V
for t
the line low for t
master must test the logical state of the 1-Wire line at
t
The t
t
expired, the DS28E01-100 is ready for data communi-
cation. In a mixed population network, t
extended to minimum 480µs at standard speed and
MSP
PDLMAX
ILMAX
PDH
.
RSTH
past the threshold V
and then transmits a presence pulse by pulling
, and t
window must be at least the sum of t
RSTL
RSTL
ILMAX
TH
is between 80µs and 480µs, the device
RECMIN
PDL
is no longer than 80µs, the device
is crossed, the DS28E01-100 waits
PUP
. To detect a presence pulse, the
is relevant for the DS28E01-100
below the threshold V
. Immediately after t
TH
1-Wire Signaling
RSTL
. The time it takes for the
duration of 480µs or
RSTH
Maxim Integrated
RSTL
PUP
should be
TL
PDHMAX
RSTH
. To get
+ t
) used
PUP
F
to
is
,