Comparison of different machine cycles in 8085 Microprocessor


So far we have come across OF, MR, MW, IOR, and IOW machine cycles. The other possible machine cycles in 8085 are BI (bus idle) and INA (interrupt acknowledge) machine cycles. Now the differences between some of the machine cycles are presented in the following tables.

Difference between OF and MR

1. Number of T states in case for OF is 4, Number of T states in case for MR is 3

2. In case of OF address can be sent out from PC. Whereas in case of MR it can be sent from BC, PC, DE, HL etc.

3. In case of OF, PC can be incremented by 1, whereas only 1 when PC be incremented by 1.

Difference between MR and MW

1. In case of MR status of S1=1 and S0=0, and in case of MW, S1=0 and S0=0.

2. In case of MR, the address floats during T2 it is for output of data during T2.

Difference between MW and IOW

1. In case of MW the address is sent out from SP, BC, DE etc. whereas in case of IOW only through WZ.

2. Address duplication is not done in case of MW whereas in case of IOW it is done.

Difference between MR and IOR

1. In case of MR IO/M* signal is equal to 0 whereas for IOR it is equal to 1.

2. For MR address is sent out from PC, SP, BC, DE. But in case of IOR it is on WZ.

Difference between IOR and IOW

1. In case of IOR the status of S1 and So are S1=1 AND S0 is equal to 0 but for IOW S1 is equal to 0 and S0 is equal to 1.

2. For IOR S0 AD7-AD0 floats during T2, but for IOW it is used for data output during T2.

raja
Published on 13-Mar-2019 08:25:15
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