LSI 53C875A - Manual (Page 79)

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 , and Power 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 , and SCSI Control 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.
Table 3.1 describes the conditions that enable these pull-ups.
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.
Table 3.1 LSI53C875A Internal Pull-ups
Signal Name Pull-up Current Conditions for Pull-up
IRQ/ 25
µ
A Pull-up enabled when the IRQ mode bit (bit 3 of DCNTL
(0x3B)) is cleared.
GPIO[1:0] 25
µ
A Pull-up enabled when bits [1:0] of General Purpose Pin
Control Zero (GPCNTL0) are not set.
TEST_HSC/ 25
µ
A Pull-up enabled all the time.
TEST_RST/ 25
µ
A Pull-up enabled all the time.
TRST, TCK, TMS, TDI 25
µ
A Pull-up enabled all the time.