MPC555CME Freescale Semiconductor, MPC555CME Datasheet - Page 324

• Manufacturer Part Number: MPC555CME
• Description: KIT EVALUATION FOR MPC555
• Manufacturer: Freescale Semiconductor
• Type: Microcontrollerr

Specifications of MPC555CME

• Contents: Module Board, Installation Guide, Power Supply, Cable, Software and more
• Processor To Be Evaluated: MPC555
• Data Bus Width: 32 bit
• Interface Type: RS-232
• For Use With/related Products: MPC555
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

9.5.5 Alignment and Packaging of Transfers
MPC555
USER’S MANUAL
The MPC555 / MPC556 external bus requires natural address alignment:
The MPC555 / MPC556 performs operand transfers through its 32-bit data port. If the
transfer is controlled by the internal memory controller, the MPC555 / MPC556 can
support 8- and 16-bit data port sizes.
The bus requires that the portion of the data bus used for a transfer to or from a par-
ticular port size be fixed. A 32-bit port must reside on DATA[0:31], a 16-bit port must
reside on DATA[0:15], and an 8-bit port must reside on DATA[0:7]. The MPC555 /
MPC556 always tries to transfer the maximum amount of data on all bus cycles. For a
word operation, it always assumes that the port is 32 bits wide when beginning the bus
cycle.
In
used:
Figure 9-22
Figure
• Byte accesses allow any address alignment
• Half-word accesses require address bit 31 to equal zero
• Word accesses require address bits 30 – 31 to equal zero
• Burst accesses require address bits 30 – 31 to equal zero
• OP0 is the most-significant byte of a word operand and OP3 is the least-signifi-
• The two bytes of a half-word operand are either OP0 (most-significant) and OP1
• The single byte of a byte-length operand is OP0, OP1, OP2, or OP3, depending
/
cant byte.
or OP2 (most-significant) and OP3, depending on the address of the access.
on the address of the access.
0
MPC556
9-21,
OP0
OP0
OP0
illustrates the device connections on the data bus.
Figure
Figure 9-21 Internal Operand Representation
9-22,
OP1
OP1
OP1
EXTERNAL BUS INTERFACE
Table
Rev. 15 October 2000
9-2, and
OP2
OP2
OP2
Table
9-3, the following conventions are
OP3
OP3
OP3
31
Word
Half-word
Byte
MOTOROLA
9-28