Signal Descriptions 3-3
3.2 Signal Descriptions
The Signal Descriptions are divided into PCI Bus Interface Signals,SCSI
Bus Interface Signals,GPIO Signals, ROM Flash and Memory Interface
Signals,Test Interface Signals,andPower and Ground Signals.
The PCI Bus Interface Signals are subdivided into System Signals,
Address and Data Signals,Interface Control Signals,Arbitration Signals,
Error Reporting Signals, and Interrupt Signal.
The SCSI Bus Interface Signals are subdivided into SCSI Bus Interface
Signals,SCSI Signals,andSCSIControl Signals.
Signals are assigned a type. There are five signal types:

3.2.1 Internal Pull-ups on LSI53C875A Signals

Several signals in the LSI53C875A have internal pull-up resistors.
Tabl e 3.1 describes the conditions that enable these pul l-ups.
IInput, a standard input onlysignal.
OOutput, a standard outputdriver (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.
Table 3.1 LSI53C875A Internal Pull-ups
Signal Name Pull-up Current Conditionsfor Pull-up
IRQ/ 25 µA Pull-up enabled when the IRQ mode bit (bit 3 of DCNTL
(0x3B)) is cleared.
GPIO[1:0] 25 µA Pull-up enabledwhen bits [1:0] of General Pur pose Pin
Control Zero (GPCNTL0) are not set.
TEST_HSC/ 25 µA Pull-up enabledall the time.
TEST_RST/ 25 µA Pull-up enabled all the time.
TRST,TCK,TMS,TDI 25µA Pull-up enabledall the time.