GD32F403xx User Manual
590
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
16-bit access operation is being performed. EXMC_NIOWR and EXMC_NIORD dictate
whether the on-going operation is a write or read operation, and EXMC_NREG is low
during IO space access.
AHB access on 16-bit PC/CF card:
1.
Common space: It is usually where data are stored, it could be accessible either in byte
or in half -word mode, and odd address access is not supported in byte mode. When AHB
word access is selected, EXMC automatically splits it into 2 consecutive half -word
access. EXMC_NREG is high when common memory is targeted. EXMC_NOE and
EXMC_NWE are the read and write enable signal for this type of access.
2.
Attribute space: It is usually where conf iguration inf ormation are stored, f or byte AHB
access, only even address is possible. Half -word access converts into a single byte
access automatically, and word access is converted into two consecutive byte access
where only the even bytes are operational. In both half -word and word access, only
EXMC_NCE3_0 will be active. EXMC_NREG is low when attribute memory is targeted.
EXMC_NOE and EXMC_NWE are the read and write enable signal f or this type of
access.
3.
IO space: Both byte and half -word AHB access are supported, in IO space memory
access, EXMC_NIORD and EXMC_NIOWR act as the read and write enable signal
respectively.