Texas Instruments OMAP36 Series, Техническое справочное руководство

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L4 Interconnects
NOTE: There is no specific error signal for the protection violation that goes out from the L4
interconnects. The out-band error that goes to the system control module indicates a
protection violation, but it also indicates normal interconnect errors.
9.3.3.4.2.3 Time-Out
This section gives information about all modules and features in the high-tier device. To flag interconnect
response being blocked, the time-out of target agents attached to unavailable modules can be enabled
with the lowest setting.
A time-out mechanism can be enabled on a per-target basis in the L4_TA_AGENT_CONTROL_L register.
If the mechanism is enabled for a TA, and commands are not accepted or responses are not returned
within the expected delay, the L4 interconnect generates an error event.
The error is logged in the target agent REQ_TIMEOUT bit L4_TA_AGENT_STATUS_L [8]. The affected
TA enters an error state that causes it to send error responses to any new request targeted at it. To
recover from this state, the TA must be reset by system software. The time-out is counted starting from
the moment a command is presented to the target, regardless of how the target responds to the
command.
The L4 interconnect implements a centralized time-base circuit that broadcasts a set of four periodic pulse
signals to all connected TAs. These four signals are referred to as 1X-time base, 4X-time base, 16X-time
base, and 64X-time base.
The time-base circuit offers four possible sets of time-base signals. Selection is done by programming
TIMEOUT_BASE field
L4_LA_NETWORK_CONTROL_L [10:8]. Table 9-117 lists the values in the number
of L4 clock cycles.
Table 9-117. L4 Time-Out Link and TA Programming
REQ_TIMEOUT[2:0]
TIMEOUT_BASE[2:0] 0 1 2 3 4
0 All L4 time-out features are disabled.
1 Locally disabled 64 256 1024 4096
2 256 1024 4096 16384
3 1024 4096 16384 65536
4 4096 16384 65536 262144
The reset value is 0x4, resulting in the longest possible time-out.
The selected time-base signals are available at any TA. Each TA can be programmed to refer to one of
these four time-base signals, by using REQ_TIMEOUT field
L4_TA_AGENT_CONTROL_L [10:8] (see
Table 9-118 ).
Table 9-118. L4 Time-Out TA Programming
REQ_TIMEOUT Target Agent Time-Out Reference
0 Time-out locally disabled
1 1X-base cycle
2 4X-base cycle
3 16X-base cycle
4 64X-base cycle
A time-out condition is detected when the command acceptance or the response is not received after a
delay of between one and three time-base periods.
Example:
• L4 frequency = 100 MHz
• TIMEOUT_BASE = 4 in the L4_LA_NETWORK_CONTROL_L register
• REQ_TIMEOUT = 2 in the L4_TA_AGENT_CONTROL_L for target agent A
2071 SWPU177N – December 2009 – Revised November 2010 Interconnect
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