Intel Embedded Intel486 User Manual

EMBEDDED Intel486™ PROCESSOR HARDWARE REFERENCE MANUAL
3-4
Figure 3-3. Ultra-Low Power Intel486™ SX and Ultra-Low Power Intel486 GX Processors
Block Diagram
Signals from the external 32-bit processor bus reach the internal units through the bus interface
unit. On the internal side, the bus interface unit and cache unit pass addresses bi-directionally
through a 32-bit bus. Data is passed from the cache to the bus interface unit on a 32-bit data bus.
The closely coupled cache and instruction prefetch units simultaneously receive instruction
prefetches from the bus interface unit over a shared 32-bit data bus, which the cache also uses to
receive operands and other types of data. Instructions in the cache are accessible to the instruction
prefetch unit, which contains a 32-byte queue of instructions waiting to be executed.
The on-chip cache is 16 Kbytes for the IntelDX4 processor and 8 Kbytes for all other members
of the Intel486 processor family. It is 4-way set associative and follows a write-through policy.
The Write-Back Enhanced IntelDX4 processor can be set to use an on-chip write-back cache pol-
Paging
Unit
Prefetcher
32-Byte Code
Queue

2x16 Bytes
Code
Stream
Barrel
Shifter
24
Cache Unit
Burst Bus
Control
Bus Control
Write Buffers
4 x 32
64-Bit Interunit Transfer Bus
Register
File
ALU
Segmentation
Unit
Descriptor
Registers
Limit and
Attribute PLA
32
Base/
Index
Bus
Translation
Lookaside
Buffer
20
8 Kbyte
Cache
Clock
Control
Control &
Protection
Test Unit
Control
ROM
Address
Drivers
CLK
Core
Clock
32
32
Data Bus
Transceivers
32
Request
Sequencer
Bus Size
Control (on
ULP486 SX
only)
Cache
Control
Parity
Generation
and Control
Boundary
Scan
Control
Bus Interface
D31-D0 on ULP486™ SX
D15-D0 on ULP486™ GX
A31-A2
BE3#- BE0#
ADS# W/R# D/C# M/IO#
PCD PWT RDY# LOCK#
PLOCK# BOFF# A20M#
BREQ HOLD HLDA
RESET SRESET INTR
NMI SMI# SMIACT#
FERR# IGNNE#
STPCLK#
A5440-01
BRDY# BLAST#
BS16# BS8# (not present
on ULP486 GX)
KEN# FLUSH#
AHOLD EADS#
DP3-DP0 PCHK# on
ULP486 SX
DP1-DP0 PCHK# on
ULP486 GX
TCK TMS
TDI TD0
128
Instruction
Decode
32
Decoded
Instruction
Path
PCD
PWT
2
Physical
Address
32-Bit Data Bus
32-Bit Data Bus
Linear Address
Micro-
Instruction
Displacement Bus
32

Intel Embedded Intel486 Specifications

General

Brand	Intel
Model	Embedded Intel486
Category	Computer Hardware
Language	English