External Bus Interface (EBI)
Freescale Semiconductor
30-37
PXR40 Microcontroller Reference Manual, Rev. 1
Figure 30-28. 32-Byte Write Cycle with External D_TA, Basic Timing
30.4.2.6.3
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 2nd 4-word burst
access is calculated by adding 0x10 to the lower 5 bits of the 1st address (no carry), and then masking out
the lower 4 bits to fix them at zero.
Table 30-15. 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
D_ADD_DAT is valid
D_ADD_DAT is valid
D_ADD_DAT is valid
D_CLKOUT
D_ADD[9:30]
D_TS
D_TA
D_RD_WR
D_BDIP
CS[n]
A
A + 4
A + 8
A + 0xc
This extra cycle is required after accesses 2, 4, and 6 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**
*
D_ADD_DAT[0:31]
D_WE
Summary of Contents for PXR4030
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