34.9.2.3 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.

Table 34-3. SMC Multiplexed Signal Translation
Signal Name	32-bit Bus			16-bit Bus		8-bit Bus
Device Type	1 x 32-bit	2 x 16-bit	4 x 8-bit	1 x 16-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	–	–	–

For 32-bit devices, bits A0 and A1 are unused. For 16-bit devices, bit A0 of address is unused. When the Byte Select option is selected, NWR1 to NWR3 are unused. When the Byte Write option is selected, NBS0 to NBS3 are unused.

Figure 34-7. Connection of 2x16-bit Data Bus on a 32-bit Data Bus (Byte Select Option)