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M E M O R Y C O N T R O L L E R
Bus turnaround
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219
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B u s t u r n a r o u n d
The memory controller can be configured for each memory bank to use external bus
turnaround cycles between read and write memory accesses. The
WAITTURN
field
can be programmed for 1 to 16 turnaround wait states, to avoid bus contention on
the external memory databus. Bus turnaround cycles are generated between
external bus transfers as follows:
Read to read (different memory banks)
Read to write (same memory bank)
Read to write (different memory banks)
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B u s t u r n a r o u n d : T i m i n g a n d p a r a m e t e r s
This section shows bus turnaround timing diagrams and parameters.
Read followed by
write with no
turnaround
This diagram shows a zero wait read followed by a zero wait write with default
turnaround between the transfers of two cycles because of the timing of the AHB
transfers. Standard AHB wait states are added to the transfers, five for the read and
three for the write.
Timing parameter
Value
WAITRD
0
WAITOEN
0
WAITPAGE
N/A
WAITWR
0
WAITWEN
0
WAITTURN
0
B
A
0
D(A)
D(B)
clk_out
addr
data
st_oe_n
cs[n]
st_we-n
Summary of Contents for NS9215
Page 1: ...NS9215 Hardware Reference 90000847_C Release date 10 April 2008...
Page 3: ......
Page 4: ......
Page 26: ...26 Hardware Reference NS9215...
Page 44: ...P I N O U T 26 5 System clock 44 Hardware Reference NS9215 System clock drawing...
Page 52: ...P I N O U T 26 5 Power and ground 52 Hardware Reference NS9215...
Page 80: ...I O C O N T ROL M O D U L E Memory Bus Configuration register 80 Hardware Reference NS9215...
Page 136: ...WOR KI N G W I TH T H E C P U Noncachable instruction fetches 136 Hardware Reference NS9215...
Page 202: ...S Y S T E M C O N T RO L M OD U L E RTC Module Control register 202 Hardware Reference NS9215...
Page 354: ...E X T E R N A L D M A DMA Peripheral Chip Select register 354 Hardware Reference NS9215...
Page 472: ...R E A L TI M E C L O C K M O D U L E General Status register 472 Hardware Reference NS9215...
Page 512: ...TI M I NG Clock timing 512 Hardware Reference NS9215...
Page 515: ...PA CKA GING Processor Dimensions www digiembedded com 515...
Page 516: ...PA CKA GING Processor Dimensions 516 Hardware Reference NS9215...