Rainbow Electronics AT91CAP9S250A - Manual (Page 174)

174
6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
Figure 22-6. Connection of 2 x 8-bit Devices on a 16-bit Bus: Byte Write Option
22.7.2.3 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 22-3
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 A1
NWR0
NRD
NCS[3]
Write Enable
Read Enable
Memory Enable
NWR1
Write Enable
Read Enable
Memory Enable
D[7:0] D[7:0]
D[15:8]
D[15:8]
A[24:2]
A[23:1]
A[23:1]
A[0]
A[0]