MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
361
Preliminary—Subject to Change Without Notice
13.5.2.8
Arbitration
The external bus design provides for a single bus master at any one time, either the MCU or an external
device. One of the external devices on the bus can have the capability of becoming bus master for the
external bus. Bus arbitration may be handled either by an external central bus arbiter or by the internal
on-chip arbiter. The arbitration configuration (external or internal) is set via the EARB bit in the
EBI_MCR.
Each bus master must have Bus Request, Bus Grant, and Bus Busy
signals. The signals are described in
detail in
Section 13.3.2, “Detailed Signal Descriptions
. The device that needs the bus asserts the Bus
Request (BR) signal. The device then waits for the arbiter to assert the Bus Grant (BG) signal. In addition,
the new master must look at the Bus Busy (BB) signal to ensure that no other master is driving the bus
before it can assert Bus Busy to assume ownership of the bus. The new master must sample Bus Busy
negated for two cycles before asserting Bus Busy, to avoid any potential conflicts. Any time the arbiter has
Table 13-18. Data Bus Requirements for Read Cycles
Transfer
Size
TSIZ[0:1]
Address
32-Bit Port Size
16-Bit Port Size
1
A30
A31
D0:D7
D8:D15
D16:D23
D24:D31
D0:D7
2
D8:D15
3
Byte
01
0
0
OP0
-
-
-
OP0
-
01
0
1
-
OP1
-
-
-
OP1
01
1
0
-
-
OP2
-
OP2
-
01
1
1
-
-
-
OP3
-
OP3
16-bit
10
0
0
OP0
OP1
-
-
OP0
OP1
10
1
0
-
-
OP2
OP3
OP2
OP3
32-bit
00
0
0
OP0
OP1
OP2
OP3
OP0/OP2
4
OP1/OP3
1
Also applies when DBM=1 for 16-bit data bus mode.
2
For address/data muxed transfers, DATA[16:23] are used externally, not DATA[0:7].
3
For address/data muxed transfers, DATA[24:31] are used externally, not DATA[8:15].
4
This case consists of two 16-bit external transactions, the first fetching OP0 and OP1, the second fetching
OP2 and OP3.
Table 13-19. Data Bus Contents for Write Cycles
Transfer
Size
TSIZ[0:1]
Address
32-Bit Port Size
16-Bit Port Size
1
A30
A31
D0:D7
D8:D15
D16:D23
D24:D31
D0:D7
2
D8:D15
3
Byte
01
0
0
OP0
-
-
-
OP0
-
01
0
1
OP1
OP1
-
-
-
OP1
01
1
0
OP2
-
OP2
-
OP2
-
01
1
1
OP3
OP3
-
OP3
-
OP3
16-bit
10
0
0
OP0
OP1
-
-
OP0
OP1
10
1
0
OP2
OP3
OP2
OP3
OP2
OP3
32-bit
00
0
0
OP0
OP1
OP2
OP3
OP0/OP2
4
OP1/OP3
1
Also applies when DBM=1 for 16-bit data bus mode.
2
For address/data muxed transfers, DATA[16:23] are used externally, not DATA[0:7].
3
For address/data muxed transfers, DATA[24:31] are used externally, not DATA[8:15].
4
This case consists of two 16-bit external transactions, the first writing OP0 and OP1, the second writing OP2
and OP3.
Содержание MPC5632M
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