Freescale Semiconductor MPC5553 - Page 498

MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor 12-49
Table 12-22 shows the truth table for the internal arbiter protocol.
Table 12-21. Internal Arbiter State Descriptions
State Description Outputs
MCU Owner Idle MCU owns bus, but is not currently running a transaction BG
=1, BB=hiZ
Ext. Owner Ext. master owns bus, may or may not be running a transaction BG
=0, BB=hiZ
MCU Bus Wait MCU owns bus for next transaction, waiting for ext. owner to negate BB
from current transaction in progress
BG =1, BB=hiZ
MCU Owner Busy MCU owns bus, and is currently running a transaction BG
=1, BB=0/1
Ext. Bus Wait Ext. master owns bus for next transaction, waiting for MCU to negate
BB
from current transaction in progress
BG =0, BB=0/1
Table 12-22. Internal Arbiter Truth Table
State
Outputs Inputs
Next State
BG BB
1
BR
2
(previ
ous)
BB
3
(previ
ous)
MCU
Internal
Request
Pending
(IRP)
4
(previous)
External
has
Higher
Priority
(EHP)
5
MCU Ext.
Transaction
in Progress
(or starting
next cycle)
(ETP)
6
Recent
BG
(RBG)
7
MCU Owner Idle 1 hiZ 1 X 0 0 0 X
8
MCU Owner Idle
MCU Owner Idle 1 hiZ X X 0 1 0 X
9
Ext. Owner
MCU Owner Idle 1 hiZ 0 X 0 X 0 X Ext. Owner
MCU Owner Idle 1 hiZ 0 X X 1 0 X Ext. Owner
MCU Owner Idle 1 hiZ X X 1 0 X X MCU Owner
Busy
MCU Owner Idle 1 hiZ 1 X 1 X X X MCU Owner
Busy
MCU Owner Idle 1 hiZ X X X X 1 X MCU Owner
Busy
Ext. Owner 0 hiZ X X 0 X X
10
X
11
Ext. Owner
Ext. Owner 0 hiZ 0 X X 1 X X Ext. Owner
Ext. Owner 0 hiZ X X 1 0 X X MCU Bus Wait
Ext. Owner 0 hiZ 1 X 1 X X X MCU Bus Wait
MCU Bus Wait 1 hiZ X 0 X
12
XX
10
X MCU Bus Wait
MCU Bus Wait 1 hiZ X X X X X 1 MCU Bus Wait
MCU Bus Wait 1 hiZ X 1 X X X 0 MCU Owner
Busy