Solutions Q8
Q 8 a) Draw & Explain interfacing of 8087 NDP with 8086. [07 M]
Ans :
-Co-processor 8087 is connected to 8086, 8086 operates in maximum mode, Hence, MN / \overline{MX} is grounded.
-8284 provides common CLK, RESET, READY signals, 8284 are used to latch the address, 8286 are used as data transceiver reaches 8288 generates control signals using S2, S1, S0 as input from the currently active processor 8259 PIC is used to accept the interrupt from 8087 & send it to the μp.
– Only 8086 can fetch instruction, but these instruction also enter 8017, 8087 treats 8086 instruction as NOP.
– ESC is used as prefix for 8087 instruction. When an instructions with ESC prefix is encountered, 8087 is activated. The ESC instruction is decoded by both 8086 & 8087.
-If ESC is present 8087 executes the instruction & 8086 discard it. If ESC not present then, 8086 executes the instructions 8087 discard it.
-During execution, if 8087 need to read/write more data from the memory, then it does 30 by stealing bus cycle from the up in following manner.
The \overline{RQ} \;/\;\overline{GT} of 8087 is connected to \overline{RR} \;/\;\overline{GT} of the μp.
-8087 gives an active low request pulse. 8086 complete the current bus cycle & gives the grant pulse & enters the Hold state. 8087 uses the shared system bus to perform the data transfer with the memory. 8087 gives the release pulse & returns the system bus back to μp.
-If 8086 requires the result of 8087 operation, it first executes the WAIT instruction. WAIT makes the μp check the ( \overline{TEST} ) pin. If the ( \overline{TEST} ) pin is high ( 8087 is BUSY), then the μp enters WAIT state.
-It comes out of it only when TEST is low (8087 has finished its execution).Thus 8086 get the correct result of 8087 operation.
Q 8 b) Explain closely coupled & loosely coupled microprocessor system. [06 M]
Ans :
Closely Coupled System :
-A closely coupled system is a system architecture & computing method in which all hardware and software components are linked together so that every component is dependent on the others. Closely Coupled system architecture encourages application & code interdependence. It is most commonly used in business system & application they rely on the interconnections inter-processing of two or more system at the same time to offer a cohesive & integrated solutions.
-If Multiple system in a closely coupled system transmit a task, the entire system would typically require to be powered down to resolve a serious hardware issue. For instance, a tightly coupled system would need to be shut down in a multi processing environment where multiple computers Share the workload to add or replace a system.
-The logic of a tightly coupled system is typically distributed among multiple hardware & software components, all of which must be functioning & connected to deliver the business logic & process. For instance a bank ATM relies on the hardware, built in firmware & applications, and the main banking app to enable a consumer to withdraw cash or use ATM – specific services.
Loosely Coupled System :
-A multiprocessor is that which contains more than two processor in a system. A system is known as a loosely connected multiprocessor, if there is a very low degree of coupling between CPU ‘s . Every CPU has local memory, collection of input – output devices & channel and arbitrator switch (CAS ) in a loosely coupled system. A computer module is a term used to describe the CPU along with its local memory, set of input output devices & CAS.
-Process that run on various computer module exchange message with one another via a physical section of this message transfer system (MTS). The term distributed system also refer to a loosely coupled system. A loosely coupled system is effective when the interaction between the processes running on various computer module are minimal.