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MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
12-42
Freescale Semiconductor
Figure 12-28. 32-Byte Write Cycle with External TA, Basic Timing
12.4.2.6.3
Small Access Example #3: 32-byte Read to 32-bit Port with BL = 1
shows an example of a 32-byte read to a 32-bit burst enabled port with burst length of 4
words, requiring two 16-byte external transactions. For this case, the address for the second 4-word burst
access is calculated by adding 0x10 to the lower 5 bits of the first address (no carry), and then masking out
the lower 4 bits to fix them at zero.
Table 12-17. Examples of 4-word Burst Addresses
1st Address
Lower 5 bits of 1st A
0x10 (no carry)
Final 2nd Address (After
Masking Lower 4 Bits)
0x000
0x10
0x10
0x008
0x18
0x10
0x010
0x00
0x00
0x018
0x08
0x00
0x020
0x30
0x30
0x028
0x38
0x30
0x030
0x20
0x20
0x038
0x28
0x20
DATA is valid
DATA is valid
CLKOUT
ADDR[8:31]
TS
DATA[0:31]
TA
RD_
WR
TSIZ[0:1]
BDIP
WE
CS
x
A
A+4
A+8
A+0xc
00
DATA is valid
This extra cycle is required after accesses 2, 4, and 6 in order to get the next 64-bits of internal write data.
*
Four more external accesses (not shown) are required to complete the internal 32-byte request.
The timing of these is the same as accesses 1-4 shown in this diagram.
**
1
2
3
4**
*
• • •
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