1. Introduction
16
Memory and I/O Addressing
The ZT 5504 supports 512 MB or 1 GB of local memory. This memory is installed at the factory
and is not field upgradeable. The local memory is implemented as Error-Correcting Code
(ECC) SDRAM. ECC will correct single bit errors (97% of all DRAM errors are single bit errors)
and can report multiple bit errors to the operating system. How ECC errors are reported is a
BIOS setup option.
In addition to SDRAM, the ZT 5504 uses an on-board flash memory device to store the system
BIOS.
See the "
Memory Configuration
" and "
I/O Configuration
" topics in Chapter 2 for more
information.
Drone Mode
Typically, the ZT 5504 operates as the System Master from the system slot. The ZT 5504 can
also operate in Drone Mode from a peripheral slot. In Drone Mode, the CPU board receives
power from the system but it cannot communicate on the CompactPCI bus. Onboard logic uses
SYSEN# to qualify the ZT 5504's location when inserted in a peripheral slot, thereby isolating
the board from the CompactPCI bus.
The ZT 5504 can be hot swapped when operating in Drone Mode (in peripheral slots, the board
is operating in isolation from the backplane).
CAUTION:
The ZT 5504 is not intended to be hot swapped in the system slot. Hot swapping
the CPU board in the system slot may damage other boards in the system.
Power Ramp Circuitry
The ZT 5504 features a power controller with power ramp circuitry that allows the board's
voltages to be ramped in a controlled fashion. The power ramp circuitry eliminates large
voltage or current spikes caused by hot swapping boards. This controlled ramping is a
requirement of the
CompactPCI Hot Swap Specification
, PICMG 2.1, Version 1.0
.
The ZT 5504's power controller unconditionally resets the board when it detects that the 3.3V,
5V, and 12V supplies are below an acceptable operating limit. Minimum voltage thresholds for
the ZT 5504 are: 4.75V (5V supply), 3.0V (3.3V supply), and 10.0V (+12V supply).
Fault current sensing is also provided. If a board fault (short circuit) or over-current condition is
detected, the power controller removes power from the ZT 5504's components and the Health
LED on the
faceplate
turns amber. Fault protection activates if the current exceeds the
threshold for greater than 50
µ
s. The ZT 5504's fault current limits are shown in the following
table.
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