1. Microprocessor History

2. Early microprocessors
PMOS technology – slow and awkward to interface with TTL family
4 bit processor
Instructions were executed in about 20 µs.
Intel 4004 the first MP. 4K nibbles address space.
Intel can manipulate a whole byte.
16Kbytes address space
50,000 operations/second.

3. N-channel MOSFET 1970. Faster than P-MOS.
Work with +ve supply; easy to interface with TTL.
1973 Intel 8080 MP.
500,000 operations/second.
64K bytes memory.
Upward software compatible with 8008.
Other brands are MC6800, Fairchild’s F-8 etc.

4. Basic types of MP Two types Single component microprocessors
Bit sliced microprocessors
Can be cascaded to allow functioning systems with word size from 4 bits to 200 bits.

5. Single component M Computer
Composed of
A processor
read only memory (for program storage)
Read/Write memory (for data storage)
Input/output connections for interfacing
Timer as event counter
Intel 8048, Motorola 6805R2.
Oven, washing machine, dish washer etc.

6. Modern MP 8, 16, 32, 64 bits are available.
Intel 8085, Motorola 6800 – 8 bit word 16 bit address.
Intel 8088, 8086, Motorola – 16 bits word, 20 bits address.
80186 – never used.
286 – real mode and protected mode; 16MB memory
386 – paging, 4GB memory, 32 bits word
486 – math coprocessor, L1 cache

7. Modern MP Pentium Pentium Pro Pentium MMX Pentium II, III, IV RISC
64 bits i/o off the chip but process 32bits word, exception floating point processed 64 bits, cache doubled, instruction pipelining.
Pentium Pro
L2 cache, Improved pipelining
Pentium MMX
Multi-Media extensions, 57 new inter instruc mostly used for multimedia programming
Pentium II, III, IV
Pentium pro with MMX tech, increased L2 cache, full 64 bit operation
RISC
Reduced instruction set processor, uniform length instruc, faster in operation, cannot perform may different thing as CISC.

8. MP based system MP
memory
IO device

9. Basic MP architecture Fetch, decode, execute. PC increment.
First instruction is a fetch
0000H for 8085
FFFF0H for 8086, 8088
Data Bus
AF, BC, DE, HL, SP, PC
many more
Instruction
Register
Register Array
ALU
Control
Bus
control
Address Bus

10. Memory Interfacing and IO decoding

11. Interfacing needs bus
Isolation and separation of signals from different devices connected to MP.
Unidirectional
Bidirectional
LS373, 244

12. Memory map
Pictorial representation of the whole range of memory address space.
Defines which memory system is where, their sizes etc.
Address space or range.
8086 has 1M address space in minimum mode.
8085 has 64K address sspace.

13. Address Decoding
Address decoder is a digital ckt that indicates that a particular area of memory is being addressed, or pointed to, by the MP.
Absolute address decoding
Decode an address to one single output
Decode so that u can get a signal from the decoder when it receives exactly that bit pattern.
Partial address decoding
Some bits are used as don’t care so that decoder gives a signal for a range of consecutive bit patterns.

14. Absolute decoding 1 0 1 1 0 a b c d e 1 0 1 1 0 Active low o/p signal
Active low o/p signal
a b c d e
Can use decoder IC with gates to achieve exact decoded o/p
3 to 8 line dcd
o/p
Logic 1 7
8 input NAND gate implementation

15. Partial decoding
When a range of addresses are deconded then it is called partial decoding. For example, if we need to generate a control signal for an address generated by the MP within the range FFF0 – FFFF, then it is called partial decoding.
Decoder, multiplexer can be used for address decoding
A15
A14
x x x x A4

16. Bus control signals
8085
IO/M RD WR
MEMR
MEMWR
IOWR

17. Interfacing A Memory Chip
2K Byte memory
Memory address space of the chip:
8800H to 8FFFH
A14
IO/M
A15
A13
3 to 8
decoder
E1 E2 E3
A12
MEMSEL Q1
A11
A10
Memory
Chip CE D7 A9 D6
A15 A14 A13 A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0
X X X X X X X X X X X A0 D0 8
8 - F
0 - F
0 - F RD WR

18. Reading a byte from memory
Reading an Opcode 4Fh in memory location 2005H.
PC places the 16bit address 2005H of the memory location on the address bus.
Control unit sends the memory read signal (MEMR) to enable O/P buffer of the memory chip.
The value 4Fh stored in location 2005H is placed on the data bus and transferred to instruction decoder of the MP.

19. 8085 functional block diagram
External Add/data
bus(8)
Interrupt control
Serial I/O control W
Temp Reg (8) Z H
(8) L B C D E
Stack pointer
(16)
Program counter (16)
Incrementer/decrementer
Latch (16)
Reg Select
MUX
Accumu
Temp Reg
Instru
Register (8)
Flags
Instru
Decoder
Address buffer (8)
Data/Add buffer (8)
Timing & control
External
Address bus(8)

20. MP operations MP initiated Operations Internal operations
Memory/IO read/write
Internal operations
Store 8-bit data
Arithmetic and logical operations
Test for conditions
Sequence the execution of Instruction
Stack operation
Peripheral operations
Reset, Interrupt, ready and hold

21. Flag register
S : after the execution of an arithmetic operation, if bit 7 of the result is 1, then sign flag is set.
Z : bit is set if ALU operation results a zero in the Acc or registers.
AC: bit is set, when a carry is generated by bit 3 and passed on bit 4.
P: parity bit is set when the result has even number of 1s.
CY = carry is set when result generates a carry. Also a borrow flag. S Z AC P CY

22. Accumulator Hold data for manipulation (arithmetic, logical).
Whenever the operation combines two words, either arithmetically or logically, the accumulator contains one word (say A) and the other word (say B) may be contained in a register or in memory location. After the operation the result is placed in the Acc replacing the word A.
Major working register. MP can directly work on Acc.
Programmed data transfer.

23. General purpose registers
Six registers.
B, C, D, E, H and L can store 8 bit data.
They can be combined to perform some 16 bit operation.

24. ALU Arithmetic logic unit. Two input ports, one output port.
Perform AND, OR, ExOR, Add, subtract, complement, Increment, Decrement, shift left, shift right.
ALUs one temporary registers are connected to MPs internal bus from which it can take data from any registers. It can place data directly to data bus through its single output port.

25. Program counter
Its job is to keep track of what instruction is being used and what the next instruction will be.
For 8085 it is 16 bit long.
Can get data from internal bus as well as memory location.
PC automatically increments to point to the next memory during the execution of the present instruction.
PC value can be changed by some instructions.

26. Stack pointer 16 bit register acts as memory pointer.
Can save the value of the program counter for later use.
points to a region of memory which is called stack. follows LIFO algorithm.
After every stack operation SP points to next available location of the stack. Usually decrements.

27. Memory address register
PC sends address to MAR. MAR points to the location of the memory where the content is to be fetched from.
PC increments but MAR does not.
If the content is an instruction, IR decodes it. During execution if it is required to fetch another word from memory, PC is loaded with the value
PC again sends it to the MAR and fetch operation starts.

28. Instruction register
Holds instruction the microprocessor is currently being executed.
8 bit long.

29. others
Instruction decoder.
Control logic.
Internal data bus.

30. Machine cycle and Timing dia
MP works in steps of clock. Each clock cycle is called T-state.
A machine cycle is composed a few T-states and performs either read or write operations.
All MP instructions are divided into few machine cycles.
Opcode fetch
Memory read
Memory write
IO read
IO write

31. Timing diaga. of Memory cycle
CLK
A15-A8
A7-A0
Data from memory
AD7-AD0
A7-A0
Data from MPU
ALE
IO/M RD WR
MEMRD
MEMWR
READ Cycle
WRITE Cycle

32. MVI A,32H Instruction 2000H 3EH ;MVI A, 32H 2001H 32H
M1 (Opcode-fetch)
M2 (Memory Read) T1 T2 T3 T4 T1 T2 T3
A15-A8
20H; high-order address
Unspecified
20H; High-order address
AD7-AD0
00H; low-order Add
01H; low-order Add
3E; opcode
32H; Data
ALE
Status IO/M=0,S1=1,S0=1; opcode fetch
Status IO/M=0,S1=1,S0=0; data read RD 32

33. Execution time Clock frequency f = 2 MHz T-state = (1/f) = 0.5 µs
Exec time for opcode fetch= (4Tx0.5)=2 µs.
Exec time for memory read = 3Tx0.5=1.5 µs.
Exec time for instruction = 7Tx0.5 = 3.5 µs.

34. 8085 40 pin DIP. +5V 3 - 5MHz ADD BUS DATA BUS CONTROL STATUS
GND 40 20
21 – 28
HIGH ORDER
ADD BUS
X1 X2
40 pin DIP.
+5V
3 - 5MHz
ADD BUS
DATA BUS
CONTROL STATUS
POWER SUPPLY AND FREQ
EXTERNALLY INITIATED SIGNALS
SERIAL I/O PORTS
SID 5
SOD 4
TRAP 6
12 – 19
MUX ADD/ DATA BUS
RST7.5 7
RST6.5 8
RST5.5 9
INTR 10
30 ALE
29 S0
READY 35
HOLD 39
33 S1
RESET IN 36
34 IO/M’
32 RD’
INTA 11
HLDA 38
31 WR’
RESET OUT
CLK OUT

35. crystal, LC tuned, external clock ckt.
8085 has the clock generation circuit on the chip can operate maximum 3.03 MHz and 8085A-2 can operate maximum 5 MHz clock.
crystal, LC tuned, external clock ckt.
the frequency at x1x2 is divided by 2 internally. This means that in order to obtain 3.03MHz, a clock source of 6.06MHz must be connected to X1X2.
for crystals with less than 4MHz, a capacitor of 20pF should be connected X2 and ground. X1 X2
GND X1 X2

36. ADD/DATA bus Address bus 16 bits Data bus 8 bit long: AD0 to AD7Q’ OC
AD7
AD6
AD5
AD0
ALE
GND
Address bus. Lower 8 bit
Address bus. higher 8 bit A8
A15
Address bus 16 bits
A8 to A15 unidirectional. Higher 8 bit
AD0 to AD7 multiplexed with data. This pins are bidirectional when used as data bus.
Data bus 8 bit long: AD0 to AD7

37. Control signals
ALE – active high output used to latch the lower 8 address bits.
RD, WR - active low output signals.
IO/M – output signal to differentiate memory and IO operation.
S1 and S0 – status output signal. Identify various operations.
Machine cycle
IO/M’ S1 S0
Control signals
Opcode fetch 1
RD=0
Memory read
Memory write
WR=0
I/O read
I/O write
Interrupt Ackn
INTA=0
Halt Z
RD, WR =Z and INTA=1
Hold X
Reset

38. External control signals
INTR – interrupt request. Input signal
INTA – interrupt acknowledge. o/p signal.
RST7.5,RST 6.5, RST5.5 – restart interrupts. Vectored interrupts. Higher priority.
TRAP - Nonmaskable interrupt. Highest priority.
Hold – request for the control of buses. I/P signal
HLDA – Hold Acknowledge. O/P signal
READY – I/P signal. When low, Mp waits for integral number of clock cycles until it goes high.

39. Interfacing I/O devices
Port address
Two ways to interface
IO mapped I/O
Memory mapped IO
8085
IO address space 256 (i.e 28)
Memory address space 64K (i.e 216)

40. Interfacing approach Port address IO mapped IO Memory Mapped IO
An address where a buffer or latch is connected through which actual data transfer takes place between MP and IO device.
Input port or output port.
IO mapped IO
The port address of the IO devices is mapped into the IO address space
Port address is an eight bit binary number. IN/OUT instructions are used data transfer.
Memory Mapped IO
The port address of the IO device is mapped into the memory address space.
Port address is a 16 bit binary number. LDA, STA etc memory related instructions are used for data transfer.

41. Logic devices for interfacing
Tri-state buffer
At input port
74LS244: unidirectional octal buffer
74LS245: bidirectional octal buffer
Latches
At output port
74LS373: Octal D type latch
Decoder
For address decoding, port selection, but control signal
74LS138: 3-to-8 decoder most commonly used.
Encoder
For interfacing keyboard
74LS148: 8 to 3 priority encoder

42. Peripheral I/O instructions
port address: 50H
2050 D3
Let input port address is 30H
2150 DB
OUT 50H sends acc content to I/O address 50H
IN 30H reads content from I/O address 30H and
stores the value in accum

43. Device selection & Data Transfer
Decode the IO address.
Combine it with control the signal to generate a unique IO select pulse that is generated only when both signals are asserted.
Use it to activate the IO port
Address decoding can be absolute or partial
Address lines
IOR or
IOW
Decoder
NOR
Enable
To Peripherals
Data bus
Latch Or
Tri-state
Buffer

44. IN 30H instruction M1 M2 M3 21H 21H 50H 51H ALE IO/M RD MEMRD IORD T1
CLK
21H
unspecified
21H
A15-A8
Port add 30H
50H
DB from memory
AD7-AD0
Port addre
30H
51H
Data from Accumula
Port add 30H
ALE
IO/M RD
MEMRD
IORD

45. OUT 50H instruction M1 M2 M3 20H 50H 51H IO/M ALE RD MEMRD WR IOWR T1
CLK
A15-A8
20H
Port add, 50H
unspecified
AD7-AD0
50H
Port addre
Data from Accumula
51H
Port add 50H
Opcode D3
ALE
IO/M RD
MEMRD WR
IOWR

46. Interfacing LED for display
Given port add: FFH
Use octal latch as o/p port.
Steps for IO select pulse:
Decode FF
Use IO/M to make the port I/O mapped only
Use WR signal to write data to the port

47. * Power supply connection to the LED segments will be opposite.
MVI A, data
OUT FFH
HLT A7
IOADR A1 WR A0
* To interface a 7-segment display you need to decide about the type of 7-segment: common anode or common cathode
* Power supply connection to the LED segments will be opposite.
* For common cathode a 0 is sent to the respective pin to lit it up.
IO/M
IOSEL
+5 V G D7
D FF D6
Octal D- latch D0 OE

48. Interfacing DIP switches
Let port address: 07H – 00H
Partial decoding
Must use pull-up resistors.
IN 07H instruction reads a byte into accumulator from port 07H A4 A3
IO/M Q0 RD A7
3 to 8
decoder
E1 E2 E3 A6
IOSEL A5 OE D7 D1 D0
+5 V

49. Interfacing 7 segment LED
o/p address F9h A7 A6 A5 A4 A3
IO/M Q5 WR A2
3 to 8
decoder
E1 E2 E3
A7 A6 A5 A4 A3 A2 A1 A0 A1
IOSEL A0
+5V OE D7
74LS377 D6 D0
D FF
7-Segment

50. 8085 Interrupts 5 interrupt pins Maskable INTR RST5.5, RST6.5, RST7.5
Non-Maskable
TRAP: cannot be disabled by instruction.
TRAP has highest priority
Once a interrupt is serviced all interrupts except TRAP is disabled

51. TRAP cannot be disabled by instruction
Requires a High level with a leading eadge at the pin.
braches to location 0024H.
disabled at the falling edge of the signal at the pin.

52. RST7.5,6.5,5.5 can be enabled or disabled by SIM (Set Interrupt Mask).
7.5 – Leading edge. branches to 003CH.
6.5,5.5 – High level.
6.5: branches to 0034H
5.5: branches to 0020H

53. INTR Interrupt process
enable by writing EI.
mp checks INTR line at each instruction.
if INTR is high, mp completes the current instr, disables Interrupt Flip-flop, sends INTA signal.
An RST instru is inserted by INTA through external hardware.
Mp saves the memory address of the next instru into stack. Program control is transferred to CALL location. The service routine starts at CALL location.
At the end of the subroutine Int Flag is enabled again by EI instru.
The last instr of the subroutine is RET to trasfer back the prog control to its orginal address.

54. RST instructions 8 RST instructions +5v EF to data bus 1 1 1 1 1 1 1
Mnemonics
Binary code
Hex
Call Location D7 D6 D5 D4 D3 D2 D1 D0
RST0 1 C7
0000
RST1 CF
0008
RST2
0010
RST3 DF
0018
RST4 E7
0020
RST5 EF
0028
RST6 F7
0030
RST7 FF
0038
+5v 1 1
EF to data bus 1 1 1 1 1
Enable

55. Write a program to count continuously in binary with some delay between each
Count. Service routine at 8070H to flush FFH five times when the interrupt occurs (on INTR lines) with some appropriate delay between flash
Main program
Service routine
8070:
SERV: PUSH B
PUSH PSW
MVI B, 0AH
MVI A, 00H
FLASH: OUT PORT1
CALL DELAY
CMA
DCR B
JNZ FLASH
POP PSW
POP B EI
RET
LXI SP, FFFFH (stack region) EI
MVI A, 00H
NXTCNT: OUT PORT1
CALL DELAY (not defined here)
INR A
JMP NXTCNT
RST 5 code EF
+5V
Interrupt instr: EF
to data bus D7 1 1 1 1
At 0028H JMP 8070H
0028 C3
002A 80 1 1 1 D0
INTA from µP

56. Description
main program initializes stack pointer at FFFF and enables the interrupts. program will count continuously from 00 to FF with some delay between each count.
To interrupt the process, a switch at INTR us pushed.
the processor will complete the current instruction and senses the interrupt. Say the next instruction is INR A.
µP disables the interrupt flip-flop, and sends out INTA signal.
INTA enables the tri-state buffer and, and RST 5 (ie EF) is placed on the data bus.
µP saves the address of the INR A instruction on the stack at locations FFFE and FFFD, and the program is transferred to memory location The location 0028 has the JMP instruction to transfer the program to the service routine.

57. Description contd. The program jumps to the service routine at 8070.
The service routing saves the registers that are being used in the subroutine and loads the count ten in register B to output five flashes and five blanks.
the service routine enables the interrupt before returning to main program.
When the service routine executes the RET instruction, the µP retrieves the address of the instruction INR A from the stack and continues the binary counting.

58. Short Questions
Ins there a minimum pulse width required for the INTR signal?
17.5 T states. CALL requir 18T states. µP check INTR signal one clock period before the last T states.
How long can the INTR pulse stay high?
until the interrupt flip-flop is set by EI instruction in the subroutine.
Can the µP be interrupted again before the completion of the first interrupt service routine?

59. Vectored interrupts
TRAP, RST 7.5,6.5 and 5.5 do not require external instruction to jump to its call locations. these interrupts are called vectored interrupts.
maskable interrupts are enabled by two instructions: EI and SIM.

60. SIM Set Interrupt Mask. 7 SOD 6 SDE 5 XX 4 R7.5 3 MSE 2 M7.5 1 M6.5
M5.5
0=available, 1=masked
no use
0 = ignore mask bits
1 = mask bits are enabled
serial out data: ignored if bit 6 is 0
if 1, Reset 7.5
Enabling all interrupts:
EI ; enable interrupts
MVI A, 08h ; load bit patters for intr
SIM ; Enables 7.5,6.5,5.5
if 1, bit 7 is serial data out

61. RIM Read Interrupt Mask.
read to sense the pending interrupts.
RIM loads accumulator with 8 bits indicating status of the interrupt masks.
RIM can also be used to read serial data. 7
SID 6
I7.5 5
I6.5 4
I5.5 3 IE 2
M7.5 1
M6.5
M5.5
1 = pending
1 = masked
1 = Interrupt enabled
Serial input data, if any

62. RIM example
Assuming the µP is completing an RST7.5 interrupt request, check to see if RST6.5 is pending. If it is pending, enable RST6.5 without affecting any other interrupts; otherwise return to main program.
RIM ; Read interrupt mask
MOV B, A ; save mask info
ANI 20h ;check if RST6.5 is pending
JNZ NEXT ; EI
RET ; RST6.5 is not pending; return to main program
NEXT: MOV A,B ;get bit pattern; RST6.5 pending
ANI 0Dh ; enables RST6.5 by setting D1=0
ORI 08h ;enable SIM by setting D3=1
SIM
JMP SERV ; Jump service routing for RST6.5 at SERV

63. DMA Direct Memory Access HOLD HLDA
IO device can transfer data from (to) memory directly.
When µP controlled data transfer is too slow
HOLD
an input high signal to this pin initiated DMA. µP releases bus in the following machine cycle. gets back the control when HOLD is low.
HLDA
HOLD Ackn. After releasing the bus µP sends a high signal at this pin to inform the IO device.

64. DMA contd.
Usually a DMA controller sends the DMA request to MP. The processor completes the current machine cycle; floats all the bus lines, and sends a ackn signal to HLDA. DMA controller takes the control of the buses and transfer data directly to memory from the external source by-passing µP. After data transfer DMA controller sends a low signal at HOLD pin to terminate the request for DMA. MP gets back its control over the buses.
Address
MPU
DMA controller
Memory IO
control
Data Bus
HOLD
HLDA

65. 8086/8088 Architecture Seven categories of signals.
Max/min mode: min mode is used for single procss. Max mode is used for multiprocss
Test: synchronize multiple processors
Data Enable: generally connected to biriectional buffer to isolate MPU from system bus.
Data tran/rcvr: controls data flow.
IO or memory: indicates whether the proc cycle is memory operation or IO operation.
Bus High Enable: enble the higher order byte of 16 bit data
Power & clock
VCC
CLK
BHE/S7
A19/S6
A16/S3
AD15
AD0
ALE
M/IO RD WR
DEN
DT/R
MuX add
& status signals
GND
INTR
NMI
HOLD
READY
RESET
External rqst
Mux add and data buses
Response to External rqst
INTA
HOLDA
Control & status signals
Multipro envrnmnt
TEST
MN/MX

66. Max/min mode control signals
Pin
Min mode
Max mode 24
INTA
QS1: queue status signal 25
ALE
QS0: queue stat signal 26
DEN
S0: input sig to bus control 27
DT/R
S1: “ 28
M/IO
S2: “ 29 WR
Lock: to prvnt another proc from gaining control 30
HLDA
RQ/GT1: enable another processor to gain control 31
HOLD
RQ/GT0: “

67. 8086 Programming model 67

68. segment registers work together with general purpose register to access any memory value. For example if we would like to access memory at the physical address 12345h (hexadecimal), we should set the DS = 1230h and SI = 0045h. This is good, since this way we can access much more memory than with a single register that is limited to 16 bit values. CPU makes a calculation of physical address by multiplying the segment register by 10h and adding general purpose register to it (1230h * 10h + 45h = 12345h): by default BX, SI and DI registers work with DS segment register; BP and SP work with SS segment register. Other general purpose registers cannot form an effective address! also, although BX can form an effective address, BH and BL cannot.

69. special purpose registers
IP - the instruction pointer.
flags register - determines the current state of the microprocessor.
IP register always works together with CS segment register and it points to currently executing instruction.

70. Memory Access [BX + SI] [BX + DI] [BP + SI] [BP + DI]
[SI] [DI] d16 (variable offset only) [BX]
[BX + SI + d8] [BX + DI + d8] [BP + SI + d8] [BP + DI + d8]
[SI + d8] [DI + d8] [BP + d8] [BX + d8]
[BX + SI + d16] [BX + DI + d16] [BP + SI + d16] [BP + DI + d16]
[SI + d16] [DI + d16] [BP + d16] [BX + d16]

71. for example, let's assume that DS = 100, BX = 30, SI = 70
for example, let's assume that DS = 100, BX = 30, SI = 70. The following addressing mode: [BX + SI] is calculated by processor to this physical address: 100 * = by default DS segment register is used for all modes except those with BP register, for these SS segment register is used. there is an easy way to remember all those possible combinations using this chart: you can form all valid combinations by taking only one item from each column or skipping the column by not taking anything from it. as you see BX and BP never go together. SI and DI also don't go together. here are an examples of a valid addressing modes:     [BX+5]     ,     [BX+SI]     ,     [DI+BX-4]

72. 80286 16 bit Eliminates the multiplexing of buses.
Has 24 bit linear address bus support 16M bytes address directly.
Supports memory management through which it can support 1Gbytes of virtual memory.
Protects system software from user programs, protects users’ program, and restricts access to some memory regions.
Supports multiuser systems.

73. 80386/486
32 bit processor.
Support following multiuser system requirement
High speed of execution
Ability to handle different types of tasks efficiently
Large memory space that can be shared by multiuser
Appropriate memory allocations and the management of memory access
Data security and data access
Limited and selected access to part of the system
Resource sharing and management

74. 32bit non-multiplexed address bus
Can address 4G physical memory and through a memory management unit 64 (246) terabytes of virtual memory.
Two modes:real mode, and protected mode.
Execution is highly pipelined.

75. 80386 Programming model
8-general purpose registers can be accessed as 8, 16 or 32 bit
6-segment selector registers.
IP can used as 16/32 bits
Flag is 31 bits but 14 are used at present.
6 for data, 3 operation,2 io previl, 1 nested task, 2 for VM 31 15 7 AX BX CX DX SP BP SI DI CS SS DS ES FS GS IP
FLAGS

76. Temperature control

77. Internal architecture of 8085
ALU