
LTC2600/LTC2610/LTC2620
13
2600fe
OPERATION
32-bit sequence. The 32-bit word is required for daisy-
chain operation, and is also available to accommodate
microprocessors which have a minimum word width of
16 bits (2 bytes).
Daisychain Operation
The serial output of the shift register appears at the SDO
pin. Data transferred to the device from the SDI input is
delayed 32 SCK rising edges before being output at the
next SCK falling edge.
The SDO output can be used to facilitate control of multiple
serial devices from a single 3-wire serial port (i.e., SCK,
SDI and CS/LD). Such a “daisychain” series is congured
by connecting SDO of each upstream device to SDI of the
next device in the chain. The shift registers of the devices
are thus connected in series, effectively forming a single
input shift register which extends through the entire
chain. Because of this, the devices can be addressed and
controlled individually by simply concatenating their input
words; the rst instruction addresses the last device in
the chain and so forth. The SCK and CS/LD signals are
common to all devices in the series.
In use, CS/LD is rst taken low. Then the concatenated
input data is transferred to the chain, using SDI of the
rst device as the data input. When the data transfer is
complete, CS/LD is taken high, completing the instruction
sequence for all devices simultaneously. A single device
can be controlled by using the no-operation command
(1111) for the other devices in the chain.
C3
COMMAND
ADDRESS
DATA (16 BITS)
C2
C1
C0
A3
A2
A1
A0
D13
D14
D15
D12 D11 D10 D9
D8
D7 D6
D5
D4
D3
D2
D1 D0
2600 TBL01
MSB
LSB
C3
COMMAND
ADDRESS
DATA (14 BITS + 2 DON’T-CARE BITS)
C2
C1
C0
A3
A2
A1
A0
D13 D12 D11 D10 D9
D8
D7 D6
D5
D4
D3
D2
D1 D0
X
2600 TBL02
MSB
LSB
C3
COMMAND
ADDRESS
DATA (12 BITS + 4 DON’T-CARE BITS)
C2
C1
C0
A3
A2
A1
A0
D11 D10 D9
D8
D7 D6
D5
D4
D3
D2
D1 D0
X
XX
2600 TBL03
MSB
LSB
INPUT WORD (LTC2600)
INPUT WORD (LTC2610)
INPUT WORD (LTC2620)