Atmel ARM-Based Evaluation Kit AT91SAM9N12-EK AT91SAM9N12-EK Data Sheet
Product codes
AT91SAM9N12-EK
377
SAM9N12/SAM9CN11/SAM9CN12 [DATASHEET]
11063K–ATARM–05-Nov-13
30.8.2.3 Signal Multiplexing
Depending on the BAT, only the write signals or the byte select signals are used. To save IOs at the external bus
interface, control signals at the SMC interface are multiplexed.
interface, control signals at the SMC interface are multiplexed.
shows signal multiplexing depending on the
data bus width and the byte access type.
For 32-bit devices, bits A0 and A1 are unused. For 16-bit devices, bit A0 of address is unused. When Byte Select Option
is selected, NWR1 to NWR3 are unused. When Byte Write option is selected, NBS0 to NBS3 are unused.
is selected, NWR1 to NWR3 are unused. When Byte Write option is selected, NBS0 to NBS3 are unused.
Figure 30-7. Connection of 2x16-bit Data Bus on a 32-bit Data Bus (Byte Select Option)
SMC
NWE
NRD
NCS[3]
Write Enable
Read Enable
Memory Enable
NBS0
D[15:0]
D[15:0]
D[31:16]
A[25:2]
A[23:0]
Write Enable
Read Enable
Memory Enable
D[31:16]
A[23:0]
Low Byte Enable
High Byte Enable
Low Byte Enable
High Byte Enable
NBS1
NBS2
NBS3
Table 30-3. SMC Multiplexed Signal Translation
Signal Name
32-bit Bus
16-bit Bus
8-bit Bus
Device Type
1x32-bit
2x16-bit
4 x 8-bit
1x16-bit
2 x 8-bit
1 x 8-bit
Byte Access Type
(BAT)
(BAT)
Byte Select
Byte Select
Byte Write
Byte Select
Byte Write
NBS0_A0
NBS0
NBS0
NBS0
A0
NWE_NWR0
NWE
NWE
NWR0
NWE
NWR0
NWE
NBS1_NWR1
NBS1
NBS1
NWR1
NBS1
NWR1
NBS2_NWR2_A1
NBS2
NBS2
NWR2
A1
A1
A1
NBS3_NWR3
NBS3
NBS3
NWR3