![ARTERY AT32F435 Series Reference Manual Download Page 526](http://html1.mh-extra.com/html/artery/at32f435-series/at32f435-series_reference-manual_2977592526.webp)
AT32F435/437
Series Reference Manual
2022.11.11
Page 526
Rev 2.03
modes supported by XMC.
Table 24-33
Data access width vs. external mem ory data width
Memory
Mode
AHB data width
Memory width
Description
8-bit NAND
R/W
8
8
R/W
16
8
Split into 2 XMC accesses
R/W
32
8
Split into 4 XMC accesses
16-bit NAND
R
8
16
R/W
16
16
R/W
32
16
Split into 4 XMC accesses
24.4.5 Access timings
The XMC access the NAND Flash according to the timing parameters, as shown in Table 24-34
and
Figure 24-19. Users can perform programming operations according to the specifications of the external
memory and application needs.
Table 24-34
NAND param eter registers
Parameter register
Function
Access mode
Unit
RGDHIZT/SPDHIZT
Number of cycles during which the
data bus is kept in high-Z state
W
HCLK cycle
RGST/SPST
Memory set up time
R/W
HCLK cycle
RGWT/SPWT
Memory set up time
R/W
HCLK cycle
RGHT/SPHT
Memory set up time
R/W
HCLK cycle
Figure 24-19
NAND read access
XMC_A[17:16]
XMC_NCE[2]
XMC_D[15
:
0]
High-Z
1
HCLK
ALE/CLE
Chip select
signal
Data from XMC
XMC_NWE
XMC_NOE
High
RGST+2
HCLK
RGWT+1
HCLK
RGHT
HCLK
NRE
Data
signals
XMC_D[15
:
0]
High-Z
XMC_NWE
XMC_NOE
High
NRE
Data
signals
If write
Data from external
memory
If read
XMC capture
data
When the NWEN bit is enabled, the XMC will monitor whether the XMC_NWAIT signal is pulled low or
not at the end of memory hold-up period, if so, it will keep the XMC_NCE[2] low until the XMC_NWAIT
goes high.
Some NAND Flash devices require that, after receiving the last address byte, that the XMC_NCE[2]
remains low until it enters ready state. This can be done by means of a special timing register and NWEN
bits: