MPC555
/
MPC556
EXTERNAL BUS INTERFACE
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
9-15
or bus arbitration to intervene between the transfers. If any of the transactions except
the first is re-tried during an access to a small port, then an exception is generated to
the RCPU.
Figure 9-10 Single Beat 32-Bit Data
Write Cycle Timing, 16 Bit-Port Size
9.5.3 Burst Transfer
The MPC555
/ MPC556 uses non-wrapping burst transfers to access operands of up
to 16 bytes (four words). A non-wrapping burst access stops accessing the external
device when the word address is modulo four. The MPC555
/ MPC556 begins the ac-
cess by supplying a starting address that points to one of the words and requiring the
memory device to sequentially drive or sample each word on the data bus. The select-
CLKOUT
ADDR[0:1]
TS
BR
BG
BB
Data
TA
RD/WR
BURST, BDIP
TSIZ[0:1]
00
10
ADDR
ADDR + 2
ABCDEFGH
EFGHEFGH
STS
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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