Intel 21555 User Manual

21555 Non-Transparent PCI-to-PCI Bridge User Manual 13
Preface
1.4 Signal Nomenclature
21555 device signal names are printed in lowercase type. Prefixes and suffixes are tagged with a leading or trailing
letter and are delimited with an “_” underscore:
• The prefix “p_” denotes a primary bus signal. For example: p_ad is the primary interface address/data bus.
• The prefix “s_” denotes a secondary bus signal. For example: s_ad is the secondary interface address/data bus.
• Other prefixes might appear. l_(load), pr_(parallel rom), and so on.
• The suffix “_l” means that the condition is qualified when that signal is low or approximately zero (0) volts.
For example: p_frame_l is a low-asserted signal.
• If no suffix is applied, it means that the condition is qualified when the signal is high or approximately equal to
vcc. For example: p_idsel is a high-asserted signal.
PCI signals that can be on either the primary interface or the secondary interface are printed in uppercase, normal
type. The names of low-asserted signals are followed by #. For example, “asserting FRAME#” can refer to the
assertion of the p_frame_l signal when the transaction is occurring on the primary bus or the assertion of the
s_frame_l signal when the transaction is occurring on the secondary bus.
Table 1 describes the Signal Type letters that appear in Table 6 through Table 10 in Chapter 3, “Signal
Descriptions”.
Table 1. Signal Type Abbreviations
Signal
Type
Description
I Standard input only.
O Standard output only.
TS Tristate bidirectional.
STS
Sustained tristate. Active low signal must be pulled high for one clock
cycle when deasserting.
OD Standard open drain.

Intel 21555 Specifications

General

Brand	Intel
Model	21555
Category	Network Hardware
Language	English