what is 8087?
8087 is a co- processor. it is also known as numeric processor. Two main sections are there in 8087
(i) CU & (ii) NEU
(i) CU (Control Unit) : All the instruction is received by the CU and decode here. It can read and write memory operand . CU also help to make a good communication system between control processor unit of 8086 and the memory.
(ii) NEU (Numeric Extension Unit) : This part helps the execution process of all the numeric processor instruction.
>> Pin Details of 8087 :
(i) AD15 to AD0 : Address and data lines. At the T1 state carry the address and At the T2,T3,TW,T4 states these lines carry the data.
(ii) A19/S6 - A16/S3 : Address and status lines as like 8086 microprocessor , S3 ,S4 and S6 are permanently high, while S5 is permanently low.
(iii) BHE /S7 : This pin is used to enable the data on the higher order address(At the T1 state) but it act as thr status line S7(At the T2 - T4 states).
(iv) QS1 and QS0 : The Queue status input signals enable he 8087 to keep track of the instruction queue status of the 8086.
(v) INT : This is an output pin. Interrupt is used to indicate that unmasked exception (such as error type or over flow or divided by 0).
(vi) BUSY : This pin indicates that co rocessor is busy with the execution of an instrction. this is coonnected to the TEST input of the 8086.
(vii) READY : This pin is used to send the signal to the co-processor that the address device such as the memory or the I/O device will complete the data transfer fromits side.
(viii) RESET : This is an input pin. it is used to discard the internal activities of the co-processor and prepare it for further execution.
(ix) CLK : this input pin provides the basic timing for the co-processor.
(x) Vcc : supply input voltage(+5V).
(xi) GND : this pin is used as the return line for the Vcc supply.
(xii) S2, S1,and S0 : these pins is used by the bus controllers to derive the Read and Write signals.
these pins can be either output pins of 8087 or input pins of 8086.
S2 S1 S0 Status
0 X X unused
1 0 0 unused
1 0 1 Memory Read
1 1 0 Memory Write
1 1 1 passive
(xiii) RQ/ GT0 : It is a bidirectional pin. This pin control the gain of the bus from the host 8086 for operand or data transfer. This pins are connected to the of request/grant pin of 8086.
(xiv) RQ/GT1 : This bidrectional pin is used by the other bus master to convey their need for local bus access to the 8087. The reqest/grant pins may be used by other bus masters such as DMA (Direct Memory Access) controllers.