16-Bit-Wide Memory Interface
10-26
10.7 16-Bit-Wide Memory Interface

The ’C32 memory interface to 16-bit-wide external memory uses STRBx_B3 pin

as an additional address pin, A–1, while using STRBx_B0 and STRBx_B1 as

strobe byte-enable pins as shown in Figure 10–14. Note that the external-

memory address pins are connected to the ’C32 address pins A22A21...A1A0A1.

In this manner, the ’C32 can read/write a single 32-, 16-, or 8-bit value from the

external 16-bit-wide memory.

Figure 10–14. External-Memory Interface for 16-Bit SRAMs

A23
A22
A21
.
.
.
A1
A0
STRBx_B3/A–1
R/W
A23
A22
.
.
.
A2
A1
A0
WE
CS
I/O(7-0)
A23
A22
.
.
.
A2
A1
A0
WE
CS
I/O(7-0)
’C32
STRBx_B2
STRBx_B1
STRBx_B0
D(31-24)
D(23-16)
D(15-8)
D(7-0)

Case 4: 16-Bit-Wide Memory With 8-Bit Data-Type Size

When the data type size is 8 bits, the ’C32 shifts the internal address two bits

to the right before presenting it to the external-address pins. In this shift, the

memory interface copies the value of the internal-address A23 to the external-

address pins A23, A22, and A21. The memory interface also copies the value

of the internal-address A1 to the external STRBx_B3/A–1 pin. Furthermore, the

memory interface activates the STRBx_B1 and STRBx_B0 pins according to

the value of the internal address bit A0 as shown in Table 10–10. Figure 10–15

shows a functional diagram of the memory interface for 16-bit-wide memory

with 8-bit data-type size.