User manual

Table Of Contents
Zynq-7000 AP SoC Technical Reference Manual www.xilinx.com 706
UG585 (v1.11) September 27, 2016
Chapter 26: Reset System
26.4 PL Resets
26.4.1 PL General Purpose User Resets
There are four separate reset signals, FCLKRESETN[3:0], routed to the PL which could be used as
general purpose reset signals for PL logic. These reset signals are not removed until the PS is out of
its boot sequence and user code de-asserts them. They are controllable by the slcr.FPGA_RST_CTRL
register. SLCR.FPGA_RST_CTRL. PL logic connecting to the PS must not be reset when active bus
transactions exist, since uncompleted transactions could be left pending in the PS.
The reset signal is loosely associated with the FCLK of the same number, however, the timing is such
that it must be considered an asynchronous reset to the PL. If the user requires a synchronized reset,
the user must synchronize it themselves in the PL. (The FCLK needs to be toggling for the reset to
propagate out of the PS.)
26.5 Register Overview
The following sections provide an overview of the reset control registers.
26.5.1 Persistent Registers
All registers are reset when the PS_POR_B reset signal is asserted. There are several registers and
register bits that persist through a non-POR reset (PS_SRST, watchdog, etc.). The persistent registers
are listed in Table 26-2.
Note: POR required to unlock slcr.SCL [LOCK] register bit, affecting: SCL, PSS_RST_CTRL, APU_CTRL,
and WDT_CLK_SEL.