K60P100M100SF2RM Datasheet, PDF (697/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Chapter 29 External Bus Interface (FlexBus)
29.2.7 Transfer Size (FB_TSIZ[1:0])
For memory accesses, these signals, along with FB_TBST, indicate the data transfer size
of the current bus operation. The interface supports 8-, 16-, and 32-bit operand transfers
and allows accesses to 8-, 16-, and 32-bit data ports.
For misaligned transfers, FB_TSIZ[1:0] indicates the size of each transfer. For example,
if a 32-bit access through a 32-bit port device occurs at a misaligned offset of 0x1, 8 bits
is transferred first (FB_TSIZ[1:0] = 01), 16 bits is transferred next at offset 0x2
(FB_TSIZ[1:0] = 10), and the final 8 bits is transferred at offset 0x4 (FB_TSIZ[1:0] =
01).
For aligned transfers larger than the port size, FB_TSIZ[1:0] behaves as follows:
• If bursting is used, FB_TSIZ[1:0] is driven to the transfer size.
• If bursting is inhibited, FB_TSIZ[1:0] first shows the entire transfer size and then
shows the port size.
FB_TSIZ[1:0]
00
01
10
11
Table 29-2. Data Transfer Size
Transfer Size
4 bytes
1 byte
2 bytes
16 bytes (line)
For burst-inhibited transfers, FB_TSIZ[1:0] changes with each FB_TS assertion to reflect
the next transfer size. For transfers to port sizes smaller than the transfer size,
FB_TSIZ[1:0] indicates the size of the entire transfer on the first access and the size of
the current port transfer on subsequent transfers. For example, for a 32-bit write to an 8-
bit port, FB_TSIZ[1:0] equals 00 for the first transaction and 01 for the next three
transactions. If bursting is used for a 32-bit write to an 8-bit port, FB_TSIZ[1:0] is driven
to 00 for the entire transfer.
29.2.8 Transfer Burst (FB_TBST)
Transfer burst indicates that a burst transfer is in progress as driven by the device. A burst
transfer can be two to 16 beats depending on FB_TSIZ[1:0] and the port size.
K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.
697