
4–6 Chapter 4: Functional Description
Clocking and Reset Structure
RapidIO II MegaCore Function August 2014 Altera Corporation
User Guide
The assertion of
rst_n
causes the whole RapidIO II IP core to reset. The requirement
that the reset controller
reset
input signal and the TX PLL
pll_powerdown
and
mcgb_rst
input signals be asserted with
rst_n
ensures that the PHY IP core resets
with the RapidIO II IP core.
User logic must assert the Transceiver PHY Reset Controller IP core
reset
signal with
rst_n
. However, each signal is deasserted synchronously with its corresponding
clock. Figure 4–2 shows a circuit that ensures these conditions. In this figure,
clock
is
the Transceiver PHY Reset Controller IP core input clock. You can extend this logic as
appropriate to include any additional reset signals.
In systems generated by Qsys, this circuit is generated automatically. However, if
your RapidIO II IP core variation is not generated by Qsys, you must implement logic
to ensure that
rst_n
and
reset
are driven from the same source, and that each meets
the minimal hold time and synchronous deassertion requirements.
While the module is held in reset, the Avalon-MM
waitrequest
outputs are driven
high and all other outputs are driven low. When the module comes out of the reset
state, all buffers are empty. Refer to Chapter 6, Software Interface for the default value
of registers after reset.
For more information about the requirements for reset signals, refer to Chapter 5,
Signals.
Consistent with normal operation, following the reset sequence, the Initialization
state machine transitions to the SILENT state. In this state, the transmitters are turned
off.
If two communicating RapidIO II IP cores are reset one after the other, one of the IP
cores may enter the Input Error Stopped state because the other IP core is in the SILENT
state while this one is already initialized. The initialized IP core enters the Input Error
Stopped state and subsequently recovers.
f For details of the RapidIO Initialization state machine, refer to section 4.12, Port
Initialization, of Part 6: LP-Serial Physical Layer Specification of the RapidIO Interconnect
Specification, Revision 2.2, available at www.rapidio.org.
Figure 4–2. Circuit to Also Ensure Synchronous Assertion of reset with rst_n
DDQ Q
rst_nrst_n
V
CC
sys_clk
clock
rst
rst_n
RapidIO II
IP Core
Transceiver
PHY Reset
Controller
IP Core
DDQ
Q
rstrst
V
CC
reset
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