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AT32F435/437
Series Reference Manual
2022.11.11
Page 523
Rev 2.03
Figure 24-16
NOR/PSRAM multiplexed mode write access
XMC_A[25
:
16]
XMC_LB
XMC_UB
XMC_NE[x]
XMC_NOE
XMC_NWE
XMC_D[15
:
0]
1
HCLK
Data from XMC
1
HCLK
DTST+2
HCLK
High
High-Z
Memory address[25:16]
XMC_NADV
1
HCLK
Don
t care
Address signals
Data signals
Chip select
signal
Memory address[15:0]
Address data
multiplex signal
24.4.2.4 Synchronous mode
As configured in Table 24-30 and Table 24-31,
the XMC uses synchronous mode to access the external
memories.
If the memory inserts XMC_NWAIT signal between the address latch and data transfer, the XMC will not
only wait (DTLAT+1) CLK clock cycles but also have to take into account the XMC_NWAIT signal. During
data transmission, the XMC will, depending on the NWTCFG configuration, select to wait either one
cycle after the XMC_NWAIT signal is active or when the XMC_NWAIT signal is active.
Figure 24-17
shows the timing for read access, while Figure 24-18 shows the timing for write access.
and Figure 24-18 are examples of XMC waiting in the next cycle of XMC_NWAIT signal
(NWTCFG=0)
Table 24-30
Synchronous mode — SRAM/NOR Flash chip select control register
Bit
Description
Configuration
Bit 31: 20
Reserved
0x0
Bit 19
MWMC: Memory write mode control
0x1
Bit 18: 16
CRPGS
:
CRAM page size
Configure according to memory specifications.
Bit 15
NWASEN: NWAIT in asynchronous
transfer enable
0x0
Bit 14
RWTD: Read-write timing different
0x0
Bit 13
NWSEN: NWAIT in synchronous
transfer enable
Configure according to memory specifications.
Bit 12
WEN: Write enable
Configure according to needs.
Bit 11
NWTCFG: NWAIT timing configuration Configure according to memory specifications.
Bit 10
WRAPEN: Wrapped enable
Configure according to needs.
Bit 9
NWPOL: NWAIT polarity
c
Bit 8
SYNCBEN: Synchronous burst enable 0x1
Bit 7
Reserved
0x1
Bit 6
NOREN: NOR
Flash access enable
Write synchronization: 0x0
Read synchronization: Configure according to memory
specifications.
Bit 5: 4
EXTMDBW: External memory data
bus width
Configure according to memory specifications.
Bit 3: 2
DEV: Memory device type
Write synchronization: 0x1
Read synchronization: Configure according to memory
specifications. It is valid except 0x0 (SRAM)
Bit 1
ADMUXEN: Address/data multiplexing
enable
Configure according to needs.