Answer:
A) 2.56 ms
B) 128 μs
Explanation:
Time for Bus cycles = 500 ns
Transfer of bus control = 250 ns
I/0 device data transfer rate = 50 KB/s
Data are transferred at : 1 byte at a time
A) Determine how long the device tie up the bus when transferring a block of 128 bytes
Block size to be transferred = 128 bytes
Bandwidth = 50 KB/s
data transfer = (Block size ) / ( Bandwidth)
= ( 128 * 8 ) / ( 50 * 10^3 * 8 )
= ( 1024 ) / ( 50 * 10^3 * 8 )
= 2.56 ms
To determine the actual transfer time we have to add up the transfer time for the bus control in both directions :
2.56 ms + 500 ns = 2.56 ms. this is because 500 ns is not a significant value
B) cycle stealing mode
In this mode each byte is transferred at a time and The total transfer time needed for the bus control in both directions will be double the total time i.e 2 * 500 ns = 1000 ns. because additional control time of 250 ns is required at both ends
since 1 byte is transferred at a time , 1 byte will be transferred in 1 μs
128 bytes = 128 * 1 μs = 128 μs