Configuration
10-14
By setting the bit fields of the STRB0 bus control register with a physical-
memory width of 32 bits and a data type size of 32 bits, the external address
referring to the STRB0 location is identical to the internal address used by the
‘C32 CPU. Alternatively, setting the bit fields of the STRB1 bus control register
with a physical memory width of 16-bit and a data-type size of 16-bit, the ad-
dress presented by the ‘C32 external pins is the internal address shifted right
by one bit with A
23
driving A
23
and A
22
. Since the STRB1 memory-bank address
pins A
23
A
22
A
21
...A
1
A
0
are connected to the ‘C32 address pins A
22
A
21
...A
1
A
0
A
–1
,
the address seen by the STRB1 memory bank is identical to the ‘C32 CPU
internal address.
Table 10–2. Data-Access Sequence for a Memory Configuration with Two Banks
ÁÁÁÁÁÁ
Á
ÁÁÁÁ
Á
ÁÁÁÁÁÁ
Instruction #
ÁÁÁÁÁÁ
Á
ÁÁÁÁ
Á
ÁÁÁÁÁÁ
Internal
Address Bus
ÁÁÁÁÁÁ
Á
ÁÁÁÁ
Á
ÁÁÁÁÁÁ
External
Address Pins
ÁÁÁÁÁÁÁÁÁ
Á
ÁÁÁÁÁÁÁ
Á
ÁÁÁÁÁÁÁÁÁ
Active Strobe Byte Enable
ÁÁÁÁÁÁÁ
Á
ÁÁÁÁÁ
Á
ÁÁÁÁÁÁÁ
Accessed
Data Pins
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
(2)
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
4000h
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
4000h
ÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁ
STRB0_B0 / B1 / B2 / B3
ÁÁÁÁ
ÁÁÁÁ
D
31–0
ÁÁÁÁ
ÁÁÁÁ
4000h
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
(3)
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
4001h
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
4001h
ÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁ
STRB0_B0 / B1 / B2 / B3
ÁÁÁÁ
ÁÁÁÁ
D
31–0
ÁÁÁÁ
ÁÁÁÁ
4001h
ÁÁÁÁÁÁ
Á
ÁÁÁÁ
Á
ÁÁÁÁÁÁ
(4)
ÁÁÁÁÁÁ
Á
ÁÁÁÁ
Á
ÁÁÁÁÁÁ
4002h
ÁÁÁÁÁÁ
Á
ÁÁÁÁ
Á
ÁÁÁÁÁÁ
4002h
ÁÁÁÁÁÁÁÁÁ
Á
ÁÁÁÁÁÁÁ
Á
ÁÁÁÁÁÁÁÁÁ
STRB0_B0 / B1 / B2 / B3
ÁÁÁÁ
Á
ÁÁ
Á
ÁÁÁÁ
D
31–0
ÁÁÁÁ
Á
ÁÁ
Á
ÁÁÁÁ
4002h
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
(5)
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
4003h
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
4003h
ÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁ
STRB0_B0 / B1 / B2 / B3
ÁÁÁÁ
ÁÁÁÁ
D
31–0
ÁÁÁÁ
ÁÁÁÁ
4003h
ÁÁÁÁÁÁ
Á
ÁÁÁÁ
Á
ÁÁÁÁÁÁ
(8)
ÁÁÁÁÁÁ
Á
ÁÁÁÁ
Á
ÁÁÁÁÁÁ
900000h
ÁÁÁÁÁÁ
Á
ÁÁÁÁ
Á
ÁÁÁÁÁÁ
C80000h
ÁÁÁÁÁÁÁÁÁ
Á
ÁÁÁÁÁÁÁ
Á
ÁÁÁÁÁÁÁÁÁ
STRB1_B0 / B1 and
STRB1_B3 / A–1 = 0
ÁÁÁÁ
Á
ÁÁ
Á
ÁÁÁÁ
D
15–0
ÁÁÁÁ
Á
ÁÁ
Á
ÁÁÁÁ
900000h
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
(9)
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
900001h
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
C80001h
ÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁ
STRB1_B0 / B1 and
ÁÁÁÁ
ÁÁÁÁ
D
15–0
ÁÁÁÁ
ÁÁÁÁ
900001h
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
ÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁ
ÁÁÁÁÁÁÁÁÁ
STRB1_B3 / A–1 = 1
ÁÁÁÁ
ÁÁÁÁ
ÁÁÁÁ
ÁÁÁÁ
The ability of the ‘C32 device to select a single byte from a single external
memory location or combinations of bytes from several contiguous memory
locations dictates that the internal address seen by the CPU correspond to a
shifted version of the address presented to the external pins. The ’C32 external
memory interface handles this conversion automatically as long as you configure
the bus control register to match the external memory configuration present in
your hardware implementation.
As seen in Figure 2–8 on page 2-20, ’C32 handles nine different memory
access cases. The following sections discuss these cases in detail.