Revision 1.01 – April 18, 2007
NPe405H – PowerNP NPe405H Embedded Processor
Data Sheet
Pull-up and Pull-down Resistors
Pull-up and pull-down resistors are used for strapping during reset and to retain unused or undriven inputs in an
appropriate state. The recommended pull-up value of 3kΩ to +3.3V (10kΩ to +5V can be used on 5V tolerant I/Os)
and pull-down value of 1kΩ to GND, applies only to individually terminated signals. To prevent possible damage to
the device, I/Os capable of becoming outputs must never be tied together and terminated through a common
resistor.
If your system-level test methodology permits, input-only signals can be connected together and terminated
through either a common resistor or directly to +3.3V or GND. When a resistor is used, its value must ensure that
the grouped I/Os reach a valid logic zero or logic one state when accounting for the total input current into the
NPe405H.
Unused I/Os
Strapping of some pins may be necessary when they are unused. Although the NPe405H requires only the pull-up
and pull-down terminations as specified in the “Signal Functional Description” on page 43, good design practice is
to terminate all unused inputs or to configure I/Os such that they always drive. If unused, the peripheral, SDRAM,
and PCI buses should be configured and terminated as follows:
•
•
•
Peripheral interface—PerAddr00:31, PerData00:31, and all of the control signals are driven by default. Ter-
minate PerReady high and PerError low.
SDRAM—Program SDRAM0_CFG[EMDULR]=1 and SDRAM0_CFG[DCE]=1. This causes the NPe405H
to actively drive all of the SDRAM address, data, and control signals.
PCI—Configure the PCI controller to park on the bus and actively drive PCIAD31:0, PCIC3:0[BE3:0], and
the remaining PCI control signals by doing the following:
- Strap the NPe405H to disable the internal PCI arbiter.
- Individually connect PCISErr, PCIPErr, PCITRDY, and PCIStop through 3.3kΩ resistors to +3.3V.
- Terminate PCIReq1:5 to +3.3V.
- Terminate PCIReq0[Gnt] to GND.
External Peripheral Bus Control Signals
All external peripheral bus control signals (PerCS0:7, PerR/W, PerWBE0:3, PerOE, PerWE, PerBLast, HoldAck,
ExtAck) are set to the high-impedance state when ExtReset=0. In addition, as detailed in the PowerNP NPe405H
Embedded Processor User’s Manual, the peripheral bus controller can be programmed via EBC0_CFG to float
some of these control signals between transactions or when an external master owns the peripheral bus. As a
result, a pull-up resistor should be added to those control signals where an undriven state may affect any devices
receiving that particular signal.
The following table lists all of the I/O signals provided by the NPe405H. Please see “Signals Listed Alphabetically”
on page 15 for the pin number to which each signal is assigned. In cases where a multiplexed signal (indicated by
the square brackets) is shown without the other signals that are assigned to that pin, you can see what the other
signals are by referring to the same table.
42
DS2011
AMCC Proprietary
AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
