Information Technology Reference
In-Depth Information
READY?
Device
1
Device
2
STATUS
DATA
Device 1 wants to
send data to Device 2
HIGH
READY?
LOW
HIGH
STATUS
LOW
Device 2 is
not busy
Device 2 is
busy
Device 2 has
read the data
Figure 2.5
Simple handshaking of data
Control lines
Control lines define the operation of the data transaction, such as:
•
Data flow direction - this identifies that data is either being read from a device or writ-
ten to a device.
•
Memory addressing type - this is typically either by identifying that the address access
is direct memory accessing or indirect memory access. This identifies that the address on
the bus is either a real memory location or is an address tag.
•
Device arbitration - this identifies which device has control of the bus, and is typically
used when there are many devices connected to a common bus, and any of the devices
are allowed to communicate with any other of the devices on the bus.
2.1.4 Cables
The cable type used to transmit the data over the bus depends on several parameters, includ-
ing:
•
The signal bandwidth.
•
The reliability of the cable.
•
The maximum length between nodes.
•
The possibility of electrical hazards.
•
Power loss in the cables.
