TC1796
System Units (Vol. 1 of 2)
LMB External Bus Unit
User’s Manual 13-8 V2.0, 2007-07
EBU, V2.0
Two components that are equipped with the EBU arbitration protocol can be directly
connected together (without additional external logic) as shown below:
Figure 13-3 Connection of Bus Arbitration Signals
Note: In the example of Figure 13-3, it is possible for the EBU to perform the function or
either Arbiter or Participant (or indeed both the Arbiter and Participant may be the
EBU).
Table 13-5 lists the programmable parameters for the external bus arbitration.
Table 13-4 EBU External Bus Arbitration Signals
Signal Direction Function
HOLD In HOLD is asserted (low) by an external bus master when the
external bus master requests to obtain ownership of the
external bus from the EBU.
HLDA In/Out
1)
HLDA is asserted (low) by the Arbiter to signal that the
external bus is available for use by the Participant (i.e. the bus
is not being used by the Arbiter). HLDA is sampled by the
Participant to detect when it may use the external bus.
BREQ Out BREQ is asserted (low) by the EBU when the EBU requests
to obtain ownership of the external bus.
1) The direction of this signal depends upon the mode in which the EBU is operating (see Page 13-10).
HOLD
HLDA
BREQ
Arbiter User
BREQ
HLDA
HOLD
MCA05714
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