Datasheet
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 A01
³8x1´
A6 A5 A4 A3 A2 A11 A0 D7 D6 D5 D4 D2 D1 D0D3
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 A10 A0 D7 D6 D5 D4 D2 D1 D0D3
LMH0395
www.ti.com
SNLS323L –AUGUST 2010–REVISED APRIL 2013
Figure 10. SPI Daisy-Chain Write
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 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 11. SPI Daisy-Chain Read
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