NXP Semiconductors MPC5566 - Page 541

External Bus Interface (EBI)
MPC5566 Microcontroller Reference Manual, Rev. 2
12-54 Freescale Semiconductor
Table 12-22 shows a description of the states defined for the internal arbiter protocol.
Table 12-23 shows the truth table for the internal arbiter protocol.
Table 12-22. Internal Arbiter State Descriptions
State Description Outputs
MCU owner idle MCU controls the bus, but is not currently running a transaction BG
=1, BB=hiZ
External owner External master controls the bus; can be running a transaction or not BG
=0, BB=hiZ
MCU bus wait MCU controls the bus for the next transaction
Waiting for the external master to negate BB
for the current transaction in progress
BG =1, BB=hiZ
MCU owner busy MCU controls the bus
Currently running a transaction
BG
=1, BB=0 or 1
External bus wait External master controls the bus for next transaction
Waiting for MCU to negate BB for the current transaction in progress
BG
=0, BB=0 or 1
Table 12-23. Truth Table for Internal Arbiter
State
Outputs Previous Inputs External Status
Next State
BG
BB
1
BR
2
BB
3
MCU
internal
request
pending
(IRP)
4
External
has
higher
priority
(EHP)
5
MCU
external
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
External owner
MCU owner idle 1 hiZ 0 X 0 X 0 X External owner
MCU owner idle 1 hiZ 0 X X 1 0 X External 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
External owner 0 hiZ X X 0 X X
10
X
11
External owner
External owner 0 hiZ 0 X X 1 X X External owner
External owner 0 hiZ X X 1 0 X X MCU bus wait
External 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
MCU owner busy 1 0 or 1
13
1X X X 1 X
8
MCU owner busy
MCU owner busy 1 0 or 1 1 X 1 X X X MCU owner busy
MCU owner busy 1 0 or 1 X X 1 0 X X MCU owner busy
MCU owner busy 1 0 or 1 0 X X 1 1 X External bus wait