
Draft xx/xx/xx
4-16
Signal Descriptions
Rev. letter
Copyright 1999 by LSI Logic Corporation. All rights reserved.
Table 4.11
Additional Pins
Symbol
Pin No.
Ball No.
Type
Description
TESTIN
178
K2
I
Test In. When this pin is driven low, the SYM53C895 connects
all inputs and outputs to an “AND tree.” All SCSI control
signals and data lines are connected to the “AND tree.” The
output of the “AND tree” is connected to the TESTOUT pin.
This allows manufacturers to verify chip connectivity and
determine exactly which pins are not properly attached. When
the TESTIN pin is driven low, internal pull-ups are enabled on
all input, output, and bidirectional pins, all outputs and
bidirectional signals are 3-stated, and the MAC/_TESTOUT
pin is enabled. Connectivity can be tested by driving one of
the SYM53C895 pins low. The MAC/_TESTOUT pin should
respond by also driving low.
GPIO0_
FETCH/
61
T19
I/O
General Purpose I/O pin. Optionally, when driven low, this pin
indicates that the next bus request is for an op code fetch.
This pin powers up as a general purpose input.This pin has
two specific purposes in the Symbios software. The software
uses it to toggle SCSI device LEDs, turning on the LED
whenever the SYM53C895 is on the SCSI bus. The software
drives this pin low to turn on the LED, or drives it high to turn
off the LED. This signal can also be used as data I/O for serial
EEPROM access. In this case, it is used with the GPIO1 pin,
which serves as a clock.
GPIO1_
MASTER/
63
R18
I/O
General Purpose I/O pin. Optionally, when driven low, this pin
indicates that the SYM53C895 is bus master. This pin powers
up as a general purpose input. Symbios software supports
use of this signal in serial EEPROM applications, when
enabled, in combination with the GPIO0 pin. When this signal
is used as a clock for serial EEPROM access, the GPIO0 pin
serves as data.
GPIO[4:2]
67–65
P19
P18
R20
I/O
General Purpose I/O pins. GPIO4 powers up as an output.
Symbios software also supports use of this signal as the
enable line for V
PP
, the 12 Volt power supply to the external
flash memory interface. GPIO[3:2] power up as inputs.
MAC/_
TESTOUT
79
K19
T/S
Memory Access Control. This pin can be programmed to
indicate local or system memory accesses (non-PCI
applications). It is also used to test the connectivity of the
SYM53C895 signals using “AND tree” scheme. The
MAC/_TESTOUT pin is only driven as the Test Out function
when the TESTIN/ pin is driven low.