Serial RapidIO (SRIO) User's Guide

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2.3.10 Reset and Power Down
SRIO Functional Description
The RapidIO peripheral allows independent software controlled shutdown for the logical blocks listed in
Table 26 . With the exception of BLK0_EN for the memory-mapped registers (MMRs), when the BLK n_EN
signals are deasserted, the clocks are gated to these blocks, effectively providing a shutdown function.
Table 26. Reset Hierarchy
Bus GBL BLK0 BLK1 BLK2 BLK3 BLK4 BLK5 BLK6 BLK7 BLK8
Logical Block Reset _EN _EN _EN _EN _EN _EN _EN _EN _EN _EN
DMA interface √ √
MMRs: √ √
Reset/power-
down control
registers
MMRs: √ √ √
Non-reset/power-
down control
registers
Interrupt handling √ √
unit (IHU)
Traffic flow logic √ √
Congestion √ √
control unit
(CCU)
LSU (Direct I/O √ √ √
initiator)
MAU (Direct I/O √ √ √
target)
TXU (message √ √ √
passing initiator)
RXU (message √ √ √
passing target)
Port 0 datapath √ √ √
Port 1 datapath √ √ √
Port 2 datapath √ √ √
Port 3 datapath √ √ √
Reset of the SERDES macros is handled independently of the registers discussed in this section. The
SERDES can be configured to shutdown unused links or fully shutdown. SERDES TX and RX channels
may be enabled/disabled by writing to bit 0 of the SERDES_CFGTX n_CNTL and
SERDES_CFGRX n_CNTL registers. The PLL and remaining SERDES functional blocks can be controlled
by writing to the ENPLL signal in the SERDES_CFG0_CNTL register. This bit will drive the SERDES
signal input, which will gate the reference clock to these blocks internally. This reference clock is sourced
from a device pin specifically for the SERDES and is not derived from the CPU clock, thus it resets
asynchronously. ENPLL will disable all SERDES high-speed output clocks. Since these clocks are
distributed to all the links, ENPLL should only be used to completely shutdown the peripheral. It should be
noted that shutdown of SERDES links in between normal packet transmissions is not permissible for two
reasons. First, the serial RapidIO sends idle packets between data packets to maintain synchronization
and lane alignment. Without this mechanism, the RapidIO RX logic can be mis-aligned for both 1X and 4X
ports. Second, the lock time of the SERDES PLL would need to reoccur, which would slow down the
operation.
When the SERDES ENTX signal is held low, the corresponding transmitter is powered down. In this state,
both outputs, TXP and TXN, will be pulled high to VDDT.
70 Serial RapidIO (SRIO) SPRUE13A – September 2006
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