DS24B33 Maxim, DS24B33 Datasheet - Page 14

• Manufacturer Part Number: DS24B33
• Description: The DS24B33 is a 4096-bit, 1-Wire® EEPROM organized as 16 memory pages of 256 bits each
• Manufacturer: Maxim

1-Wire 4Kb EEPROM
This command can save time in a single-drop bus sys-
tem by allowing the bus master to access the memory
functions without providing the 64-bit ROM code. If
more than one slave is present on the bus and, for
example, a read command is issued following the Skip
ROM command, data collision occurs on the bus as
multiple slaves transmit simultaneously (open-drain
pulldowns produce a wired-AND result).
To maximize the data throughput in a multidrop envi-
ronment, the Resume command is available. This com-
mand checks the status of the RC bit and, if it is set,
directly transfers control to the memory functions, simi-
lar to a Skip ROM command. The only way to set the
RC bit is by successfully executing the Match ROM,
Search ROM, or Overdrive-Match ROM command.
Once the RC bit is set, the device can repeatedly 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 ROM code. Unlike the
normal Skip ROM command, the Overdrive-Skip ROM
command sets the DS24B33 in 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 devices on the bus to stan-
dard speed (OD = 0).
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Overdrive-Skip ROM [3Ch]
Skip ROM [CCh]
Resume [A5h]
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 ROM sequence transmitted at overdrive speed
allows the bus master to address a specific DS24B33
on a multidrop bus and to simultaneously set it in over-
drive mode. Only the DS24B33 that exactly matches
the 64-bit ROM sequence responds to the subsequent
memory function command. Slaves already in overdrive
mode from a previous Overdrive-Skip ROM or success-
ful Overdrive-Match ROM command remain in over-
drive 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.
Overdrive-Match ROM [69h]