Datasheet

(host)

SCK

(host)

16xN clocks

Device N-1

Read Data

Device 1

Read Data

Device N

Read Data

MOSI

(host)

'21¶7&$5(

SPI Read Data

16xN clocks

³16x1´ ³16x1´ ³16x1´

Device N

Read Data

Device N-1

Read Data

Device 1

Read Data

SPI Read Data

MISO

(host)

A6 A5 A4 A3 A2 A1 A01

³8x1´

A6 A5 A4 A3 A2 A11 A0 D7 D6 D5 D4 D2 D1 D0D3

LMH0394

www.ti.com

SNLS312L –AUGUST 2010–REVISED APRIL 2013

SPI Daisy-Chain Read

Figure 9 shows the SPI daisy-chain read for a daisy-chain of N devices. The SPI daisy-chain read is 32xN bits

long, consisting of 16xN bits for the read transaction followed by 16xN bits for the dummy read transaction (all

“1”s) to shift out the read data on the MISO output. The SS signal is driven low and SCK is toggled for 16xN

clocks. The first 16xN bit MOSI payload (sent to Device 1 in the daisy-chain) consists of the 16-bit SPI read data

for Device N (the last device in the chain), followed by the read data for Device N-1, Device N-2, etc., ending with

the read data for Device 1 (the first device in the chain). The 16-bit SPI read data for each device consists of a

“1” (read command), seven address bits, and eight “1”s (which are ignored). After the first 16xN bit transaction,

SS must return high (to latch the data) and then is driven low again before the second 16xN bit transaction of all

“1”s is sent to the MOSI input. The requested read data is shifted out on MISO starting with the data for Device N

and ending with the data for Device 1. After this transaction, SS must return high.

Figure 9. SPI Daisy-Chain Read

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