SS

(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 A0

1

³8x1´

A6 A5 A4 A3 A2 A1

1

A0 D7 D6 D5 D4

D2 D1 D0

D3

SS

(host)

SCK

(host)

16xN clocks

Device N-1

Write Data

Device N-2

Write Data

Device N-3

Write Data

Device N

Write Data

MOSI (host)

MOSI Device 1

MISO Device 1

MOSI Device 2

'21¶7&$5(

Device 1

Write Data

Device N

Write Data

Device N-1

Write Data

Device N-2

Write Data

Device 2

Write Data

'21¶7&$5(

'21¶7&$5(

'21¶7&$5(

'21¶7&$5(

Device N

Write Data

MISO Device N-1

MOSI Device N

SPI Write Data

A6 A5 A4 A3 A2 A1

0

A0 D7 D6 D5 D4

D2 D1 D0

D3

LMH0395

SNLS323M – AUGUST 2010 – REVISED JULY 2015

www.ti.com

Programming (continued)

7.5.1.5 SPI Daisy-Chain Write

Figure 10 shows the SPI daisy-chain write for a daisy-chain of N devices. The SS signal is driven low and SCK is

toggled for 16xN clocks. The 16xN bit MOSI payload (sent to Device 1 in the daisy-chain) consists of the 16-bit

SPI write data for Device N (the last device in the chain), followed by the write data for Device –1, Device –2,

and so forth, ending with the write data for Device 1 (the first device in the chain). The 16-bit SPI write data for

each device consists of a “0” (write command), seven address bits, and eight data bits. After the SPI daisy-chain

write, SS must return high and then the write occurs for all devices in the daisy-chain.

Figure 10. SPI Daisy-Chain Write

7.5.1.6 SPI Daisy-Chain Read

Figure 11 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 –1, Device –2, and so forth,

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 11. SPI Daisy-Chain Read

16

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