GD32F10x User Manual
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period of ATTHLD, NAND Flash waits for EXMC_INTx signal to be busy, and the time period
of ATTHLD should be greater than tWB (tWB is defined as the time from EXMC_NWE high
to EXMC_INTx low). For NCE-sensitive NAND Flash, after the first command byte following
address bytes has been entered, EXMC_NCE must remain low until EXMC_INTx goes from
low to high. The ATTHLD value of attribute space can be set in EXMC_NPATCFGx register
to meet the timing requirements of tWB. CPU can use the attribute space timing when writing
the first command byte following address bytes to the NAND Flash device. In other times, the
MCU must use the common space timing.
NAND Flash ECC calculation module
An ECC calculation hardware is implemented in bank1 and bank2 respectively. Users can
choose page size according to the ECCSZ control field in the EXMC_NPCTLx register. ECC
offers one bit error correction and two bits errors detection.
When NAND memory block is enabled, ECC module will detect EXMC_D[15:0], EXMC_NCE
and EXMC_NWE signals. When a data size of ECCSZ has been read or written, software
must read the calculated ECC in the EXMC_NECCx register. When a recalculation of ECC is
needed, software must clear the EXMC_NECCx register value by resetting ECCEN bit of
EXMC_NPCTLx register to zero, and then restart ECC calculation by setting the ECCEN bit
of EXMC_NPCTLx to 1.
PC/CF Card access
EXMC Bank3 is used exclusively for PC/CF Card, both memory and IO mode access are
supported. This bank is divided further into three sub spaces, memory, attribute and IO space.
EXMC_NCE3_0 and EXMC_NCE3_1 are the byte select signals, when only EXMC_NCE3_0
is active (Low), the lower byte or upper byte is selected depending on the EXMC_A[0], while
only EXMC_NCE3_1 is active (Low), the upper byte is selected which is not supported, when
both of these signals are active, 16-bit operation is performed. When NDTP is reset to select
PC/CF Card as external memory device, NDW must be set to 01 in EXMC_NPCTLx register
to guarantee correct EXMC operation.
EXMC PC/CF card access behavior for different spaces:
1.
Common space: EXMC_NCE3_x (x = 0, 1) is the chip enable signal, it indicates whether
8- or 16-bit access operation is being performed. EXMC_NWE and EXMC_NOE dictates
whether the on-going operation is a write or read operation, and EXMC_NREG is high
during common space access.
2.
Attribute space: EXMC_NCE3_x (x = 0, 1) is the chip enable signal, it indicates whether
8- or 16-bit access operation is being performed. EXMC_NWE and EXMC_NOE dictates
whether the on-going operation is a write or read operation, and EXMC_NREG is low
during attribute space access.
3.
IO space: EXMC_NCE3_x (x = 0, 1) is the chip enable signal, it indicates whether 8- or
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