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GD32F403xx User Manual
566
HADDR [17:16] bits are used to select one of the three areas.
–
When HADDR [17:16] = 00, the data area is selected.
–
When HADDR [17:16] = 01, the command area is selected.
–
When HADDR [17:16] = 1X, the address area is selected.
Application software uses these three areas to access NAND Flash, their definitions are as
f ollows.
–
Address area: This area is where the NAND Flash access address should be issued by
sof tware, the EXMC will pull the address latch enable (ALE) signal automatically in
address transfer phase. ALE is mapped to EXMC_A [17].
–
Command area: This area is where the NAND Flash access command should be issued
by the software, the EXMC will pull the command latch enable (CLE) signal automatically
in command transfer phase. CLE is mapped to EXMC_A [16].
–
Data area: This area is where the NAND Flash read/write data should be accessed.
When the EXMC is in data transfer mode, software should write the data to be transferred
to the NAND Flash in this area. When the EXMC is in data reception mode, software
should read the data from the NAND Flash by reading this area. Data access address is
incremented automatically in consecutive mode, users need not to be concerned with
access address area.
21.3.4.
NOR/PSRAM controller
NOR/PSRAM memory controller controls bank0, which is designed to support NOR Flash,
PSRAM, SRAM, ROM and honeycomb RAM external memory. EXMC has 4 independent
chip-select signals f or each of the 4 sub -banks within bank0, named NE[x] (x = 0, 1, 2, 3).
Other signals f or NOR/PSRAM access are shared. Each sub-bank has its own set of
conf iguration register.
Note:
In asynchronous mode, all output signals of controller will change on the rise edge of internal
AHB bus clock (HCLK).
In synchronous mode, all output data of controller will change on the f all edge of extern
memory device clock (EXMC_CLK).
NOR/PSRAM memory device interface description
Table 21-1. NOR Flash interface signals description
EXMC Pin
Direction
Mode
Functional description
EXMC_CLK
Output
Sync
Clock signal for sync
Non-muxed
EXMC_A[25:0]
Output
Async/Sync
Address bus signal
Muxed EXMC_A[25:16]
EXMC_D[15:0]
Input/output
Async/Sync
Address/Data bus