Rainbow Electronics W90N745CDG User Manual
Page 35
W90N745CD/W90N745CDG
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Figure 6.2.5 CPU registers Read/Write with external memory
Table 6.2.3 and Table 6.2.4
Using big-endian and word access, Program/Data path between register and external memory
WA = Address whose LSB is 0,4,8,C X = Don’t care
nWBE [1-0] / SDQM [1-0] = A means active and U means inactive
Table 6.2.3 Word access write operation with Big Endian
ACCESS OPERATION
WRITE OPERATION (CPU REGISTER Î EXTERNAL MEMORY)
XD WIDTH
HALF WORD
BYTE
Bit Number
CPU Reg Data
31 0
ABCD
31 0
ABCD
SA
WA WA
Bit Number
SD
31 0
AB CD
31 0
A B C D
Bit Number
ED
15 0
AB
15 0
CD
7 0
A
7 0
B
7 0
C
7 0
D
XA
WA WA+2 WA WA+1 WA+2 WA+3
nWBE [1-0] /
SDQM [1-0]
AA AA XA XA XA
XA
Bit Number
XD
15 0
AB
15 0
CD
7 0
A
7 0
B
7 0
C
7 0
D
Bit Number
Ext. Mem Data
15 0
AB
15 0
CD
7 0
A
7 0
B
7 0
C
7 0
D
Timing Sequence
1st write
2nd write
1st write
2nd write
3rd write
4th write