Internal Pull-Ups On Lsi53C875A Signals; Lsi53C875A Internal Pull-Ups; Scsi Signals - LSI LSI53C875A Technical Manual

3.2 Signal Descriptions

3.2.1 Internal Pull-ups on LSI53C875A Signals

Table 3.1

LSI53C875A Internal Pull-ups

Signal Name
IRQ/
GPIO[1:0]
TEST_HSC/
TEST_RST/
TRST, TCK, TMS, TDI
The Signal Descriptions are divided into
Bus Interface Signals,
Signals, Test Interface
The PCI Bus Interface Signals are subdivided into
Address and Data Signals,
Error Reporting Signals, and
The SCSI Bus Interface Signals are subdivided into
Signals, SCSI Signals, and
Signals are assigned a type. There are five signal types:
I Input, a standard input only signal.
O Output, a standard output driver (typically a Totem Pole Output).
I/O Input and output (bidirectional).
T/S 3-state, a bidirectional, 3-state input/output signal.
S/T/S Sustained 3-state, an active LOW 3-state signal owned and driven by
one and only one agent at a time.
Several signals in the LSI53C875A have internal pull-up resistors.
Table 3.1 describes the conditions that enable these pull-ups.
Pull-up Current Conditions for Pull-up
25 A Pull-up enabled when the IRQ mode bit (bit 3 of DCNTL
(0x3B)) is cleared.
25 A Pull-up enabled when bits [1:0] of
Control Zero (GPCNTL0)
25 A Pull-up enabled all the time.
25 A Pull-up enabled all the time.
25 A Pull-up enabled all the time.
Signal Descriptions
PCI Bus Interface
GPIO Signals, ROM Flash and Memory Interface
Signals, and Power and Ground
Interface Control
Interrupt Signal.
SCSI Control Signals.
Signals,
Signals.
System Signals,
Signals, Arbitration
SCSI Bus Interface
General Purpose Pin
are not set.
SCSI
Signals,
3-3