30
Virtex-6 FPGA System Monitor
UG370 (v1.1) June 14, 2010
System Monitor Control Logic
Supply Sensor Alarms
When the measured value on the supply sensor for V
CCINT
or V
CCAUX
is greater than the
thresholds in Control registers
51h
and
52h
, or less than the thresholds in Control registers
55h
and
56h
, then the output alarms go active. The alarms are reset when a subsequently
measured value falls inside the threshold.
Thermal Management
The on-chip temperature measurement is used for critical temperature warnings. The
default Over Temperature threshold is 125°C. This threshold is used for preconfiguration
or when the contents of the OT Upper alarm register have not been configured. To override
this default condition, the 10 MSBs of the OT Upper register (Control Register
53h
) must
be set using the temperature sensor transfer function (
). In addition, the four LSBs
must be set to
0011b
.
When the die temperature exceeds a factory set limit of 125°C or a user selected threshold,
the Over-Temperature alarm logic output (OT) becomes active. This feature can be
disabled by the user when System Monitor is instantiated in a design. The OT function is
disabled by writing a logic 1 to the OT bit in Configuration register 1. The OT signal resets
when the FPGA temperature has fallen below a user-programmable limit in Control
register
57h
(see
). When the automatic power-down feature is enabled,
the OT signal can be used to trigger a device power down. When OT goes active High, the
FPGA enters power down approximately 10 ms later. The power-down feature initiates a
configuration shutdown sequence disabling the device when finished and asserts GHIGH
to prevent any contention (see
Virtex-6 FPGA Configuration Guide
). When OT is deasserted,
GHIGH will also deassert and the startup sequence is initiated releasing all global
resources. By default this functionality is disabled and must be explicitly enabled. The
automatic power down is enabled by using a configuration option in the ISE™ software,
version 9.1i or later. Check the “Power Down Device if Over Safe Temperature” option
under “Configuration Options” on the Process Properties GUI for generating a
programming file. Alternatively use the
bitgen -g
command line option
OverTempPowerDown:[Enable¦Disable]
. When the FPGA enters power down,
System Monitor continues to operate in whatever mode was configured prior to power
down using an internal clock oscillator. The FPGA automatically powers up once the
temperature has fallen below the user-programmable lower limit (see
). The System Monitor OT signal can also be reset by writing a logic 1 to the OT bit
in System Monitor Configuration Register 1 via the JTAG DRP interface. On-chip sensors
Table 17:
Alarm Threshold Registers (
50h
to
57h
)
Control Register
Description
Alarm
50h
Temperature Upper
ALM[0]
51h
V
CCINT
Upper
ALM[1]
52h
V
CCAUX
Upper
ALM[2]
53h
OT Upper
OT
54h
Temperature Lower
ALM[0]
55h
V
CCINT
Lower
ALM[1]
56h
V
CCAUX
Lower
ALM[2]
57h
OT Lower
OT
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