Chapter 4: Theory of operation
63
Software must first write to the index register before reading or writing to the
data register.
Watchdog timer
The watchdog timer is a counter that can be programmed to time out and produce a
hard or soft reset. The timeout has six selections, ranging from 0.5s to 4 minutes.
The type of reset generated is selected by the Reset Control register, bit 0.
Table 4-8. CPLD indexes for function registers
Name
Index
value
R/W
Function
Reserved
0x00
—
—
Watchdog control0x01
R/W
Enable watchdog
Reserved
0x02
—
—
Front panel LED 0x03
W
Controls Red/Green LED and Blue
LED on front panel
Last reset source 0x04
R
Identifies reset source
Local interrupt
enables
0x05
R/W
Enables/disables various interrupts
from the CPLD
Reset control
0x06
R/W
Assigns Hard or Soft reset attribute to
various reset sources
HS latch status
and ENUM
0x07
R
Allow for software to determine if the
HS latch is open or if ENUM is
asserted.
BIOS page select 0x08
R/W
Selects which BIOS page is
accessible. Has write-protect bit for 7
of the 8 pages.
CompactPCI
features
0x09
R/W bit-5 only
CompactPCI geographical address,
~SYSGEN, CompactPCI interrupt
route, RTM present.
IPMI special
utility
0x0A
R/W
Allows Host to reset and program the
IPMI microntroller.
Unused
0x0B–
0x0F
—
RTM Version
0x10
R
Allows CPU to determine which RTM
is presently installed.
Subsystem ID
0x11
R
EPC-3307 subsystem ID (0x1F).
Reserved
0xFF
—
—
Undefined bits in a register will have an undefined value when read.
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