UNIT-I

UNIT-I 80386DX functional Block Diagram PIN Description Register set Flags Physical address space Data types80386DX Feature It supports 8/16/32 bit data operandsIt has 32-bit internal registersIt supports 32-bit data bus and 32-bit non-multiplexed address busIt supportsPhysical Address of 4GBVirtual Address of 64TBMaximum Segment size of 4GBIt operates in 3 different modesRealProtectedVirtual 8086MMU provides virtual memory, paging and 4 levels of protectionClock Frequency : 20,25 and 33MHzIt has 132 pin package

80386DX functional Block Diagram

Internal Architecture80386 is divided into three sections:Central Processing UnitMemory Management UnitBus Interface unit

Central Processing Unit

The CPU divided into Instruction Unit:It decodes the opcode bytes received from the 16-byte instruction queue and arranges them into a 3-decoded instruction queue.After decoding it is passed to control section for deriving necessary control signals Execution Unit:It has 8 general purpose and 8 special purpose registers which either handles data or addressesThe 64-bit barrel shifter increases the speed of all shift, rotate, multiply and divide operationsThe multiply/divide logic implements the bit-shift-rotate algorithms to complete the operations in minimum time(Even 32bit multiplication is done in 1s)

Elements of Execution Unit

Arithmetic/logic unit (ALU): Performs the operation identified by ADD, SUB, AND, etc.Flags register: Holds status and control informationGeneral-purpose registers: Holds address or data informationControl ROM: Contains microcode sequences that define operations performed by machine instructionsSpecial multiply, shift, and barrel shift hardware: Accelerate multiply, divide, and rotate operations

Memory Management Unit

It consists of a segmentation unit and paging unitSegmentation Unit:It allows the use of two address components - segment and offset for relocability and sharing of dataIt allows a maximum segment size of 4GBIt provides a 4-level protection mechanism for protecting and isolating systems code and data from those of application programThe limit and attribute PLA checks segment limits and attributes at segment level to avoid invalid accesses to code and data in memory segment.

Memory Management Unit

Paging Unit It organizes physical memory in terms of pages of 4KB sizeIt works under the control of segmentation unitIt converts linear addresses into physical addressesThe control and attribute PLA checks privileges at page level.

Bus Interface Unit

It has a prioritizer to resolve the priority of various bus requests. This controls the access of the busThe address driver drives the bus enable and address signals A2 A31.The pipeline/bus size unit handles the control signals for pipelining and dynamic bus sizing unitsThe data buffers interface the internal data bus with system bus

PIN Description

PIN Description

# symbol indicates active low signal. When no # is present, the signal is active high. Example: M/IO# - High voltage indicates memory selected- Low voltage indicates I/O selectedPIN Description

Clock (CLK2): It is divided by two internally to generate the internal processor clock. Data Bus (D0 through D31):It has three-state bidirectional signals.It can transfer data on 32- and 16-bit buses using a data bus sizing feature. Address Bus (A2 through A31)These three-state outputs provide memory or I/O port addresses.It can access 4GB of physical memory from 00000000H to FFFFFFFFHOf the total 32-bits, only higher 30 are released by MPA1 & A0 are used internally by MP to produce 4 bank enable signals(BE3# - BE0#)

PIN Description

Byte Enable Outputs( BE0# -- BE3#)enable 4 memory banksindicates which bytes of the 32-bit data bus are involved with the current transfer. BE0# applies to D0-D7BE1# applies to D8-D15BE2# applies to D16-D23BE3# applies to D24-D31No. of Byte Enables asserted indicates physical size of operand being transferred (1, 2, 3, or 4 bytes).

PIN Description

PIN Description

BE3# BE2# BE1# BE0# Operation 1 1 1 1 No Operation 1 1 1 0 Bank0 (8-bit) 1 1 0 1 Bank1 (8-bit) 1 0 1 1 Bank2 (8-bit) 0 1 1 1 Bank3 (8-bit) 1 1 0 0 Bank 0,1 (16-bit) 1 0 0 1 Bank 1,2 (16-bit) 0 0 1 1 Bank 2,3 (16-bit) 1 0 0 0 Bank 0,1,2(24-bit) 0 0 0 1 Bank 1,2,3(24-bit) 0 0 0 0 Bank 0,1,2,3 (32-bit) PIN Description

Bus Cycle Definition Signals (W/R#, D/C#, M/IO# , LOCK#)three-state outputs W/R# :distinguishes b/w write and read cycles. D/C# :distinguishes b/w data and control cycles. (interrupt, acknowledge, halt, and instruction fetching.) M/IO# :distinguishes b/w memory and I/O cycles. LOCK# :distinguishes b/w locked and unlocked bus cycles. It enables CPU to prevent other bus masters (like coprocessor) from gaining the control of system bus.

PIN Description

Bus Control Signals(ADS#,READY#,NA#,BS16#):indicates when a bus cycle has begun and allow other system hardware to control address pipelining, data bus width and bus cycle termination.ADDRESS STATUS (ADS#) : indicates that a valid address is driven at 80386DX pins. TRANSFER ACKNOWLEDGE (READY#) : indicates that the previous bus cycle is complete and bus is ready for next bus cycle. It is useful for interfacing slow peripheralsNEXT ADDRESS REQUEST (NA#) : This is used to enable address pipelining. It indicates that the system is prepared to accept the next address even if the end of current cycle is not being acknowledged on READY#. BUS SIZE 16 (BS16#) : Asserting this input constrains current bus cycle to use only D0-D15 of data bus.

PIN Description

Bus Arbitration Signals (HOLD, HLDA)HOLD : BUS HOLD REQUEST input allows another bus master to request control of the local busHLDA : BUS HOLD ACKNOWLEDGE output indicates that the Intel386 DX has surrendered control of its local bus to another bus master.PIN Description

COPROCESSOR REQUEST (PEREQ) : PROCESSOR EXTENSION REQUESTThis input signal indicates a coprocessor request for a data operand to be transferred to/from memory by Intel386 DX. COPROCESSOR BUSY (BUSY#) : - This input indicates that coprocessor is still executing an instruction and is not yet able to accept another. This sampling of BUSY# input prevents overrunning the execution of a previous coprocessor instruction.COPROCESSOR ERROR (ERROR#) : - signals an error condition from a processor extension.

PIN DescriptionInterrupt Signals (INTR, NMI, RESET)MASKABLE INTERRUPT REQUEST (INTR): is a maskable input that signals the Intel386DX to suspend execution of the current program and execute an interrupt acknowledge function.NON-MASKABLE INTERRUPT REQUEST(NMI): - non-maskable input that signals the Intel386 DX to suspend execution of the current program and execute an interrupt acknowledge function. RESET (RESET) : suspends any operation in progress and places the Intel386DX in a known reset state. See Interrupt Signals for additionalinformation.

PIN Description

RESET (RESET) : This input signal suspends any operation in progress and places the Intel386 DX in a known reset state. The Intel386 DX is reset by asserting RESET for 15 or more CLK2 periods When RESET is asserted, all other input pins are ignored, and all other bus pins are driven to an idle bus state.If RESET and HOLD are both asserted at a point in time, RESET takes priority.

PIN Description

Vcc: These are system power supply linesGND: These are return lines for the power supply

Register Set The Intel386 DX has 32 register resources in thefollowing categories: General Purpose Registers Segment Registers Instruction Pointer and Flags Control Registers System Address Registers Debug Registers Test Registers.registers are a superset of the 8086, 80186 and 80286 registers, all 16-bit 8086, 80186 and 80286 registers are contained within the 32-bit Intel386

Flag Registers

Segment Registers

Control Register

System Address Register

Debug and Test Registers