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Zynq-7000 AP SoC Technical Reference Manual www.xilinx.com 547
UG585 (v1.11) September 27, 2016
Chapter 17: SPI Controller
17.4.1 Resets
The controller has two reset domains: the APB interface and the controller itself. They can be
controlled together or independently. The effects for each reset type are summarized in Table 17-3.
Example: Reset the APB Interface and SPI 0 Controller
1. Write to the slcr reset register for SPI. Write a 1, and after some delay write a 0 to the
slcr.SPI_RST_CTRL [SPI0_REF_RST] and [SPI0_CPU1X_RST] bit fields.
17.4.2 Clocks
The core of each SPI controller is driven by the same reference clock (SPI_Ref_Clk) that is generated
by the PS clock subsystem, Chapter 25, Clocks. The APB interface is clocked by the CPU_1x clock. The
CPU_1x clock runs asynchronous to the reference clock. The operating frequency specifications for
the controller clocks are defined in the data sheet. The I/O signals are clocked synchronously by the
SCLK.
Note: Clock gating is used as power management feature for SPI. Please refer section
24.3.2 Peripherals for more details.
CPU_1x
The CPU_1x clock part of the CPU clock domain, refer section 25.2 CPU Clock.
SPI_Ref_Clk
The clock enable, PLL select and divisor settings are programmed using the slcr.SPI_CLK_CTRL
register as described in section 25.6.3 SDIO, SMC, SPI, Quad-SPI and UART Clocks.
Frequency Restriction Note: The SPI_Ref_Clk must be always be set to a higher frequency than the
CPU_1x clock frequency.
Master Mode SCLK
The SCLK is driven by the controller in master mode. It is generated by the a divided-down
SPI_Ref_Clk using the spi.Config_reg0 [BAUD_RATE_DIV] bit field.
Table 17-3: SPI Reset Effects
Name
APB
Interface
TxFIFO
and
RxFIFO
Protocol
Engine
Registers
ABP Interface Reset
slcr.SPI_RST_CTRL [SPIx_CPU1X_RST]
Yes Yes No Yes
PS Reset Subsystem
slcr.SPI_RST_CTRL [SPIx_REF_RST]
No Yes Yes No