3.2.9.2.3 Signal Multiplexing

Depending on the Byte Access Type (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. The table below shows signal multiplexing depending on the data bus width and the Byte Access Type.

For 16-bit devices, bit A0 of the address is unused. When the Byte Select option is selected, NWR1 is unused. When the Byte Write option is selected, NBS0 is unused.

Table 3-3. SMC Multiplexed Signal Translation
Device TypeSignal Name
16-bit Bus8-bit Bus
1 x 16-bit2 x 8-bit1 x 8-bit
Byte Access Type (BAT)Byte SelectByte Write–
NBS0_A0NBS0–A0
NWE_NWR0NWENWR0NWE
NBS1_NWR1NBS1NWR1–
A1A1A1A1