8-Bit-Wide Memory Interface
10-32
10.8 8-Bit-Wide Memory Interface
’C32 memory interface to an 8-bit wide external memory uses STRBx_B3 and
STRBx_B2 pins as additional address pins, A–1 and A–2, respectively, while
using STRBx_B0 as strobe byte-enable pin as shown in Figure 10–18. The
external-memory address pins are connected to the ’C32’s address pins
A21A20...A1A0A–1A–2. In this manner, the ’C32 can read/write a single 32-, 16-,
or 8-bit value from the external 8-bit-wide memory.

Figure 10–18. External Memory Interface for 8-Bit SRAMs

A23
A22
A21
.
.
A1
A0
STRBx_B2/A–2
R/W
A23
.
.
A3
A2
A0
WE
CS
I/O(7-0)
’C32
STRBx_B1
STRBx_B0
D(31-24)
D(23-16)
D(15-8)
D(7-0)
STRBx_B3/A–1 A1

Case 7: 8-Bit-Wide Memory With 8-Bit Data-Type Size

Similarly to case 4, the ’C32 shifts the internal address two bits to the right
before presenting it to the external-address pins when the data type is 8-bit. As
in case 4, the memory interface copies the value of the internal-address A23 to
the external-address pins A23, A22, and A21. But in case 7, the memory interface
also copies the value of the internal-address A1 to the external STRBx_B3/A–1
pin and the value of A0 to the external STRBx_B2/A–2. Moreover, the memory
interface only activates the STRBx_B0 pin during the external memory access.
Figure 10–19 shows a functional diagram of the memory interface for 8-bit-wide
memory with an 8-bit data-type size.