13-10
MCF5282 User’s Manual
MOTOROLA
Data Transfer Operation
13.4.6 Back-to-Back Bus Cycles
The MCF5282 runs back-to-back bus cycles whenever possible. For example, when a
longword read is started on a word-size bus, the processor performs two back-to-back word
read accesses. Back-to-back accesses are distinguished by the continuous assertion of TIP
throughout the cycle. Figure 13-11 shows a read back-to-back with a write.
Figure 13-11. Back-to-Back Bus Cycles
Basic read and write cycles are used to show a back-to-back cycle, but there is no restriction
as to the type of operations to be placed back to back. The initiation of a back-to-back cycle
is not user definable.
13.4.7 Burst Cycles
The MCF5282 can be programmed to initiate burst cycles if its transfer size exceeds the
size of the port it is transferring to. For example, a word transfer to an 8-bit port would take
a 2-byte burst cycle. A line transfer to a 32-bit port would take a 4-longword burst cycle.
The MCF5282 bus can support 2-1-1-1 burst cycles to maximize cache performance and
optimize DMA transfers. A user can add wait states by delaying termination of the cycle.
The initiation of a burst cycle is encoded on the size pins. For burst transfers to smaller port
sizes, SIZ[1:0] indicates the size of the entire transfer. For example, if the MCF5282 writes
a longword to an 8-bit port, SIZ[1:0] = 00 for the first byte transfer and does not change.
The CSCRs can be used to enable bursting for reads, writes, or both. MCF5282 memory
space can be declared burst-inhibited for reads and writes by clearing the appropriate
R/W
TIP
TS
CS
n
, BS
n
D[31:0]
TA
Read
S0
S1
S2
S3
S4
S5
S0
S1
S2
S3
S4
S5
Write
OE
CLKOUT
A[31:0], SIZ[1:0]
Summary of Contents for ColdFire MCF5281
Page 124: ...3 20 MCF5282 User s Manual MOTOROLA EMAC Instruction Set Summary ...
Page 141: ...MOTOROLA Chapter 5 Static RAM SRAM 5 5 SRAM Programming Model ...
Page 142: ...5 6 MCF5282 User s Manual MOTOROLA SRAM Programming Model ...
Page 168: ...6 26 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 186: ...7 18 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 228: ...9 22 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 246: ...10 18 MCF5282 User s Manual MOTOROLA Low Power Wakeup Operation ...
Page 254: ...11 8 MCF5282 User s Manual MOTOROLA Memory Map and Registers ...
Page 264: ...12 10 MCF5282 User s Manual MOTOROLA Chip Select Registers ...
Page 280: ...13 16 MCF5282 User s Manual MOTOROLA Misaligned Operands ...
Page 314: ...14 34 MCF5282 User s Manual MOTOROLA MCF5282 External Signals ...
Page 339: ...MOTOROLA Chapter 15 Synchronous DRAM Controller Module 15 25 SDRAM Example ...
Page 340: ...15 26 MCF5282 User s Manual MOTOROLA SDRAM Example ...
Page 356: ...16 16 MCF5282 User s Manual MOTOROLA DMA Controller Module Functional Description ...
Page 408: ...17 52 MCF5282 User s Manual MOTOROLA Buffer Descriptors ...
Page 446: ...20 24 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 474: ...22 18 MCF5282 User s Manual MOTOROLA Programming Model ...
Page 510: ...23 36 MCF5282 User s Manual MOTOROLA Operation ...
Page 526: ...24 16 MCF5282 User s Manual MOTOROLA I2C Programming Examples ...
Page 672: ...28 12 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 718: ...29 46 MCF5282 User s Manual MOTOROLA Motorola Recommended BDM Pinout ...
Page 750: ...32 8 MCF5282 User s Manual MOTOROLA Ordering Information ...