TC1796
System Units (Vol. 1 of 2)
LMB External Bus Unit
User’s Manual
13-16
V2.0, 2007-07
EBU, V2.0
Figure 13-7 Bus Ownership Control with the EBU in Participant Mode
MCA05718
EBU is in Hold Mode
The EBU remains in Hold Mode
until an PLMB access to the
external bus is received. This
access is rejected with a retry and
the EBU starts an arbitration cycle
to gain ownership of the bus.
Start
EBU access
to ext. bus is
pending?
HLDA = 0?
yes
no
EBU is in Hold Mode
yes
no
EBU is in Owner Mode
EBU access
to ext. bus is
underway?
New EBU
access to ext. bus is
waiting?
EBU_CON.
EXTLOCK = 1?
EBU access
to ext. bus is
pending?
yes
no
yes
no
yes
no
yes
no
The EBU remains in Hold Mode
until the bus is released by the
Arbiter (signalled by the HLDA = 0).
Once the EBU has gained the
external bus ownership it holds
ownership:
While EXTLOCK = 1
or
Until all queued external accesses
are completed.
or
While an PLMB access is pending
(i.e. until a time-out occurs).
When the conditions are
appropriate the EBU voluntarily
surrenders external bus ownership
to the Arbiter (regardless of the
state of the HOLD input).