Datasheet

159
SAM9261 [DATASHEET]
Atmel-6062O-ATARM-SAM9261-Datasheet_21-Jun-16
Figure 20-7. Connection of 2x16-bit Data Bus on a 32-bit Data Bus (Byte Select Option)
20.7.2.3 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. Table 20-3 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.
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 20-3. 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) 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