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LTC2373-18

237318f

For more information www.linear.com/LTC2373-18

Programming the Sequencer

Transaction Window

A transaction window opens at power-up, after resetting

the LTC2373-18, and every conversion cycle at the falling

edge of BUSY, allowing the sequencer to be programmed.

Once the transaction window opens, the state machine

controlling the programming of the sequencer memory is

in a reset state, waiting for control words to be shifted in

at SDI. The transaction window closes at the start of the

next conversion when BUSY transitions from low to high,

as shown in Figure 19. Serial input data at SDI is ignored

by the sequencer state machine when BUSY is high.

Input Control Word

The input control word is used to determine whether or

not the sequencer is being programmed. In many cases

the user will simply need to configure the converter once

for their specific application after power-up or resetting

the part, and then drive the SDI pin to GND. This will force

the control word bits to all zeros and the converter will

automatically sequence through the configurations stored

in sequencer memory. The following sections provide

further details on programming the sequencer.

The sequencer memory may be programmed by inputting

oneormorevalidcontrolwordsatSDI.Eachcontrolwordis

an8-bitwordasdescribedintheConfiguringtheLTC2373-

18 section. A valid input control word is one where C[7] = 1

and the remaining lower 7-bits, C[6:0], have been shifted

in before the transaction window closes as shown in

Figure 20a. When the 1st control word is successfully en-

teredonthe8thrisingedgeofSCK,thesequencermemory

is cleared, the new configuration, C[6:0], is written into

the first memory location and is applied to the converter.

At this point, a new acquisition window begins since the

applicaTions inForMaTion

Figure 19. Sequencer Programming Transaction Window

CNV

BUSY

TRANSACTION WINDOW

237318 F19

SEQUENCER MEMORY

7-BITS WIDE

CONTROL

WORDS

C0[6:0]

C1[6:0]

C2[6:0]

C3[6:0]

C4[6:0]

C5[6:0]

C6[6:0]

C7[6:0]

C8[6:0]

C9[6:0]

C10[6:0]

C11[6:0]

C12[6:0]

C13[6:0]

C14[6:0]

C15[6:0]

237318 F18a

Figure 18a. Internal Sequencer Memory

Figure 18b. Sequencer Programmed with Eight Control Words and the

Memory Pointer Location for Conversions Run After Programming

237318 F18b

SEQUENCER PROGRAMMED

WITH EIGHT CONTROL WORDS

MEMORY POINTER

LOCATION

....

C0[6:0]

C1[6:0]

C2[6:0]

C3[6:0]

C4[6:0]

C5[6:0]

C6[6:0]

C7[6:0]

1ST CONVERSION

2ND CONVERSION

3RD CONVERSION

4TH CONVERSION

5TH CONVERSION

6TH CONVERSION

7TH CONVERSION

8TH CONVERSION

9TH CONVERSION

10TH CONVERSION

11TH CONVERSION

12TH CONVERSION

13TH CONVERSION

14TH CONVERSION

15TH CONVERSION

16TH CONVERSION

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