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a
(T2CDELAY)
SPIx_CLK
(i)
SPIx_CLK
(ii)
SPIx_CLK
(iii)
SPIx_CLK
(iv)
b
(WDELAY)
c
(C2TDELAY)
SPIx_SCS[n]
Architecture
1436
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Serial Peripheral Interface (SPI)
29.2.20.2 SPI 4-Pin with SPIx_SCS[n] Mode
illustrates the T2CDELAY, WDELAY and C2TDELAY delays in SPI 4-pin with SPIx_SCS[n]
master mode. C2EDELAY and T2EDELAY are not available in this mode. All the three delay periods
T2CDELAY, WDELAY, and C2TDELAY proceed to completion when enabled.
Figure 29-14. SPI 4-Pin with SPIx_SCS[n] Mode with T2CDELAY, WDELAY, and C2TDELAY
29.2.20.3 SPI 4-Pin with SPIx_ENA Mode
shows the T2EDELAY and WDELAY delays in SPI 4-pin with SPIx_ENA master mode.
T2CDELAY, C2TDELAY, and C2EDELAY are not available in this mode.
•
In CASE1, the SPIx_ENA is deasserted during the T2EDELAY period. Consequently the T2EDELAY
period is terminated early (a) and the WDELAY period begins immediately (b) if enabled. The next
transfer is initiated as soon as the slave asserts SPIx_ENA again.
•
In CASE2, the T2EDELAY period (c) completes before the SPIx_ENA is deasserted. As a result the
DESYNC error is set. However since the SPIx_ENA is deasserted during the WDELAY period (d), the
master delays the next transfer until the SPIx_ENA is asserted again.
•
In CASE3, the T2EDELAY (e) and WDELAY (f) period (if enabled) both expire before the SPIx_ENA
input is deasserted. The DESYNC error is set at the end of the T2EDELAY period (e). However in this
case the master begins the next transfer immediately after it is initiated and ignores the SPIx_ENA
during the transfer even if it is subsequently deasserted.
If the T2EDELAY delay period is disabled then the DESYNC error is not set. The SPI master behavior
in this case depends on whether the SPIx_ENA gets deasserted during the WDELAY period (CASE2)
or SPIx_ENA gets deasserted after the WDELAY period completes (CASE3).