Avago Technologies LSI53C896 - Manual (Page 110)

3-22 Signal Descriptions
Version 3.3 Copyright © 1998–2003 by LSI Logic Corporation. All rights reserved.
3.7 MAD Bus Programming
The MAD[7:0] pins, in addition to serving as the address/data bus for the
local memory interface, also program power-up options for the chip. A
particular option is programmed allowing the internal pull-down current sink
to pull the pin LOW at reset or by connecting a 4.7 k
Ω
resistor between
the appropriate MAD[x] pin and V
SS
. The pull-down resistors require that
HC or HCT external components are used for the memory interface.
•
MAD[7], Serial EEPROM programmable option – When allowed to
be pulled LOW by the internal pull-down current sink, the automatic
data download is enabled. When pulled HIGH by an external resistor,
the automatic data download is disabled. Refer to
Section 2.4, “Serial EEPROM Interface,” and Subsystem ID and
Subsystem Vendor ID Registers in Chapter 4, “Registers,” for details.
•
MAD[6] – Enable B duplicate SCSI REQ/ and ACK/ signals. When
allowed to be pulled LOW by the internal pull-down current sink, the
duplicate SCSI REQ/ and ACK/ signals for channel B are disabled.
When pulled HIGH by an external resistor, the duplicate SCSI REQ/
and ACK/ signals for channel B are enabled.
•
MAD[5] – Enable A duplicate SCSI REQ/ and ACK/ signals. When
allowed to be pulled LOW by the internal pull-down current sink, the
duplicate SCSI REQ/ and ACK/ signals for channel A are disabled.
When pulled HIGH by an external resistor, the duplicate SCSI REQ/
and ACK/ signals for channel A are enabled.
•
MAD[4], INTA/ routing enable – Placing a pull-up resistor on this
pin causes SCSI Function B interrupt requests to appear on the
INTA/ pin, along with SCSI Function A interrupt requests, instead of
on INTB/. Placing a pull-up resistor on this pin also causes the SCSI
Function B Interrupt Pin register (
0x3D ) in PCI configuration space
to be programmed to 0x01 instead of 0x02.
Placing no resistor on this pin causes SCSI Function B interrupt
requests to appear on the INTB/ pin. Placing no resistor on this pin
also causes the SCSI Function B Interrupt Pin register (
0x3D ) in PCI
configuration space to be programmed to 0x02.