SN74BCT2420
NuBus ADDRESS/DATA TRANSCEIVERS AND REGISTERS
SDIS007A – D3159, NOVEMBER 1988 – REVISED JANUARY 1989
FN PACKAGE
(TOP VIEW)
• Designed for NuBus Interface
Applications
• Conforms to ANSI/IEEE Std 1196-1987
• On-Chip Comparator Provides I/D Slot
9
8
7
6
5
4
3
2
1 68 67 66 65 64 63 62 61
60
Identification
AEN 10
ID0
ALE
IDEQ
ACLK 11
ID3 12
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
• Multiplexed Real-Time and Latched
Address/Data
SSEQ 13
AD7 14
AD6 15
AD5 16
AD4 17
V
CC
• Designed to Operate With SN74ACT2440
AD15
AD14
AD13
AD12
GND
AD11
AD10
AD9
NuBus Controller
• BiCMOS Design Substantially Reduces
Standby Current
18
19
20
21
22
23
24
25
26
GND
AD3
AD2
AD1
AD0
• Dependable Texas instruments Quality and
Reliability
AD8
ID1
ADEN
DCLK
ID2
description
V
CC
A/D
DLE
DEN
The ’BCT2420 consists of bus transceiver circuits,
D-type flip-flops, latches, and control circuitry
arranged for multiplexed transmission of address
and data information in NuBus applications. An
on-chip comparator has been included to detect
when a NuBus transfer cycle is requesting the
local board. The device conforms to ANSI/IEEE
Std 1196-1987 and operates with Texas instru-
27 28 29 30 31 32 33 34 3536 37 38 39 40 41 42 43
ments SN74ACT2440 NuBus
Controller. In
addition, the device is easily configured around
ASIC or other PAL -based controllers.
The ’BCT2420 was designed using Texas Instruments BiCMOS process, which features bipolar drive
characteristics and greatly reduces the standby power of the device when disabled. This feature is especially
valuable when the device is not performing a NuBus transaction.
The AEN, DEN and ADEN inputs control the transceiver functions. Three 16-bit I/O ports, A15–A0, D15–D0,
and AD15–AD0, provide for address and data transfer. When the NuBus performs a write cycle to the local
board, address information is saved on the rising edge of ACLK. During the last portion of the NuBus write
cycle, data information is saved on the rising edge of DCLK.
When the local board is performing a write to the NuBus , address and data is multiplexed onto the NuBus
via the A/D line. Address and data can be latched by using the ALE and DLE input lines respectively.
The IDEQ output is used to signal that the local board is being requested by the NuBus . This output is typically
fedtotheNuBus controller. IDEQgoesactive(low)whenAD15–AD12arelowandAD11–AD8matchID3–ID0.
IDEQ stays valid until the next address clock (ACLK) occurs. Internal 10-kΩ pullup resistors are included on the
ID3–ID0 inputs.
The SSEQ output is used to signal the local board that super-slot addresses are being requested. This output
is active (low) whenever AD15–AD12 are equal to ID3–AD0, except when ID3–ID0 are all low.
In typical NuBus applications, two devices are required to provide the full 32-bit address/data path. Refer to
the typical NuBus interface diagram on page 9 for additional information.
The SN74BCT2420 is characterized for operation from 0°C to 70°C.
NuBus is a trademark of Texas Instruments Incorporated.
PAL is a registered trademark of Monolithic Memories Inc.
Copyright 1989, Texas Instruments Incorporated
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
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