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2016-04-28 - Giant Gecko Family - d0053_Rev1.20
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When ITS is set to 1 each memory bank uses an individual timing set. In this case registers
EBI_ADDRTIMING, EBI_RDTIMING and EBI_WRTIMING only apply to bank 0. Timing for bank n is
then defined in the EBI_ADDRTIMINGn, EBI_RDTIMINGn and EBI_WRTIMINGn registers.
Note
All timing related bitfields have a default value which is equal to the highest possible value
for these bitfields, which makes the default values a better fit for slow memory devices.
This differs from the EFM32G devices in which the default values correspond to the lowest
possible values, which would only be appropriate for fast memory devices.
14.3.11 Data Access Width
The mapping of AHB transactions to external device accesses depends on the data width of the external
device and on whether or not it supports byte lanes. The data width of external devices is specified in
the MODE and MODEn bitfields of the EBI_CTRL register. An external device is specified to be either
8-bit or 16-bit wide. Availability of byte lane support by the external device is specified via the BL and
BLn bitfields of the EBI_CTRL register. When the ITS bitfield in the EBI_CTRL register is set to 0, the
MODE and BL bitfields apply to all 4 memory banks. When ITS is set to 1 each memory bank uses an
individual mode and byte lane enable definition. In this case bitfields MODE and BL only apply to bank
0. The mode and byte lane availability for bank n is then defined in the MODEn and BLn bitfields.
In case the AHB transaction width does not match the width of the selected device, the EBI automatically
translates the AHB transaction into 1 or more external device transactions matching the capabilities
of that device. If one AHB transaction is translated into multiple external transactions, then the
external transactions have incrementing addresses and start with the lowest data byte(s) from the AHB
transaction. The translation, and possibly bus fault generation, is explained below and in Table 14.3 (p.
188) :
• If the AHB transaction width is larger than the external device width, then multiple consecutive external
transactions are performed starting with the least significant data.
• If the AHB transaction width is smaller than the external device width, then EBI behavior depends on
whether or not byte lanes are available for the selected device. Reads either use byte lane support
when available, or read according to the full external device width and disregard the superfluous data.
Writes normally either use byte lane support when available, or perform a read-modify-write sequence
to only change the required data. However, NAND Flash does not support byte lanes or random
access read-modify-write and therefore a hard fault is generated in case of an 8-bit write to a bank
designated as 16-bit NAND bank.
Table 14.3. EBI Mapping of AHB Transactions to External Device Transactions
Data Access
by Cortex-
M3, DMA, or
prefetch
8-bit External
Device (non-
NAND)
transaction(s)
16-bit External
Device (non-
NAND)
transaction(s)
(with byte lanes)
16-bit External
Device (non-
NAND)
transaction(s)
(without byte
lanes)
8-bit NAND Flash
transaction(s)
16-bit
NAND Flash
transaction(s)
8-bit read
1 x 8-bit read
1 x 8-bit read
(using byte lane)
1 x 16-bit read
1 x 8-bit read
1 x 16-bit read
16-bit read
2 x 8-bit read
1 x 16-bit read
1 x 16-bit read
2 x 8-bit read
1 x 16-bit read
32-bit read
4 x 8-bit read
2 x 16-bit read
2 x 16-bit read
4 x 8-bit read
2 x 16-bit read
8-bit write
1 x 8-bit write
1 x 8-bit write
(using byte lane)
1 x 16-bit read;
1 x 16-bit write
(read-modify-
write)
1 x 8-bit write
- (Hard fault)
16-bit write
2 x 8-bit write
1 x 16-bit write
1 x 16-bit write
2 x 8-bit write
1 x 16-bit write
32-bit write
4 x 8-bit write
2 x 16-bit write
2 x 16-bit write
4 x 8-bit write
2 x 16-bit write
Summary of Contents for Giant Gecko EFM32GG
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