Computer Hardware User's Guide

32-Bit-Wide Memory Interface
10-22
For example, reading from or writing to memory locations 904000h to
904004h involves the pins listed in Table 10–6.
Table 10–6. Example of 8-Bit Data-Type Size
Internal
Address Bus
External
Address Pins
Active Strobe
Byte Enable
Accessed
Data Pins
904000h E41000h STRB1_B0 D
7–0
904001h E41000h STRB1_B1 D
15–8
904002h E41000h STRB1_B2 D
23–16
904003h E41000h STRB1_B3 D
31–24
904004h E41001h STRB1_B0 D
7–0
Case 2: 32-Bit-Wide Memory With 16-Bit Data-Type Size
When the data-type size is 16 bits, the ’C32 shifts the internal address one bit
to the right before presenting it to the external-address pins. In this shift, the
memory interface copies the value of the internal-address A
23
to the external-
address pins A
23
and A
22
. Also, the memory interface activates the STRBX-B3
through STRBx_B0 pins according to the value of the internal address bit A
0
as shown in Table 10–7. Figure 10–12 shows a functional diagram of the
memory interface for 32-bit-wide memory with 16-bit data-type size.
Table 10–7. Strobe Byte-Enable for 32-Bit-Wide Memory With 16-Bit Data-Type Size
Internal A
0
Active Strobe Byte Enable
0 STRBx_B1 and STRBx_B0
1 STRBx_B3 and STRBx_B2