18-05-2012, 04:51 PM
THE 8088 AND 8086MICROPROCESSORS ANDTHEIR MEMORY ANDINPUT/OUTPUT INTERFACES
The 8088 and 8086 Microprocessors
The 8086, announced in 1978, was the first 16-bit microprocessor introduced by Intel Corporation
8086 and 8088 are internally 16-bit MPU.
Externally the 8086 has a 16-bit data bus and the 8088 has an 8-bit data bus
Minimum-Mode Interface
Address/Data bus
The address bus is used to carry address information to the memory and I/O ports
The address bus is 20-bit long and consists of signal lines A0 through A19
A 20-bit address gives the 8088 a 1 Mbyte memory address space
Only address line A0 through A15 are used when addressing I/O.
This give an I/O address space of 64 Kbytes
The 8088 has 8 multiplexed address/data bus lines (A0~A7)
8086 has 16 multiplexed address/data bus lines (A0~A15)
Maximum-Mode Interface
The maximum-mode configuration is mainly used for implementing a multiprocessor/coprocessor system environment
Multiple processors exist in the system
Each executes its own program
Global resources and local resources
The former are common to all processors
The latter are assigned to specific processors
In the maximum-mode, facilities are provided for implementing allocation of global resources and passing bus control to other microprocessors sharing the system bus
Electrical Characteristics
Power is applied between pin 40 (Vcc) and pins 1 (GND) and 20 (GND)
The nominal value of Vcc is specified as +5V dc with a tolerance of ±10%.
Both 8088 and 8086 draw a maximum of 340mA from the supply
Address Bus Status Codes
Whenever a memory bus cycle is in progress, an address bus status code S4S3 is output by the processor.
S4S3 identifies which one of the four segment register is used to generate the physical address in the current bus cycle: