DS2408 Maxim, DS2408 Datasheet - Page 12

• Manufacturer Part Number: DS2408
• Description: The DS2408 is an 8-channel, programmable I/O 1-Wire® chip
• Manufacturer: Maxim

Control/Status Register
The data in this register reports status information, determines the function of the RSTZ pin and further
configures the device for conditional search. This register can only be written through the Write Condi-
tional Search Registers command.
Control/Status Register Bitmap
This register is read/write. Without V
tional assignments of the individual bits are explained in the table below. Bits 4 to 6 have no function;
they will always read 0 and cannot be set to 1.
Control/Status Register Details
The interaction of the various signals that determine whether the device responds to a conditional search
is illustrated in Figure 7. The selection mask SM selects the participating channels. The polarity selection
SP determines for each channel whether the channel signal needs to be 1 or 0 to qualify. The PLS bit
determines whether all channel signals are taken from the activity latches or I/O pins. The signals of all
channels are fed into an AND gate as well as an OR gate. The CT bit finally selects the AND’ed or
OR’ed result as the conditional search response signal CSR.
Note on CT bit:
OR
AND For the qualifying condition to be met, the input (pin state or activity latch) for every selected
PLS: Pin or Activity
Latch Select
CT: Conditional Search
Logical Term
ROS: RSTZ Pin Mode
Control
PORL: Power-On Reset
Latch
VCCP: V
Status (Read-Only)
008Dh
ADDR
BIT DESCRIPTION
The qualifying condition is met if the input (pin state or activity latch) for one or more selected
channels matches the corresponding polarity.
channel must match the corresponding polarity.
CC
VCCP
Power
b7
b6
0
BIT(S)
b0
b1
b2
b3
b7
b5
0
CC
Selects either the PIO pins or the PIO activity latches as input for the
conditional search.
Specifies whether the data of two or more channels needs to be OR’ed
or AND’ed to meet the qualifying condition for the device to respond to a
conditional search. If only a single channel is selected in the channel
selection mask (008Bh) this bit is a don't care.
Configures RSTZ as either RST input or STRB output
Specifies whether the device has performed a power-on reset. This bit
can only be cleared to 0 under software control. As long as this bit is 1
the device will always respond to a conditional search.
For V
source ≥ V
b4
0
supply, this register reads 08h after a power-on reset. The func-
CC
0: pin selected (default)
1: activity latch selected
0: bitwise OR (default)
1: bitwise AND
0: configured as RST input (default)
1: configured as STRB output
0: V
1: V
powered operation the V
PORL
PUP
b3
CC
CC
12 of 39
.
pin is grounded
-powered operation
ROS
b2
DEFINITION
CT
b1
CC
pin needs to be tied to a voltage
PLS
b0
DS2408