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Under
development
Preliminary Specifications REV.B3
Specifications in this manual are tentative and subject to change.
Mitsubishi Microcomputers
M32C/83 group
SINGLE-CHIP 16/32-BIT CMOS MICROCOMPUTER
Bus Control
61
Status of external data bus
RAS
CASH
CASL
LLL
LL
H
LL
H
LLL
Read data from both even and odd addresses
Read 1 byte of data from even address
Read 1 byte of data from odd address
Write data to both even and odd addresses
Data bus width
DW
H
L
LL
H
L
LHL
L
LL
H
LL
L
8-bit
Write 1 byte of data to even address
Write 1 byte of data to odd address
Read 1 byte of data
Write 1 byte of data
16-bit
Not used
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(9) DRAM controller signals (RAS, CASL, CASH, and DW)
Bits 1, 2, and 3 of the DRAM control register (address 000416) select the DRAM space and enable the
DRAM controller. The DRAM controller signals are output when the DRAM area is accessed. Table
1.7.10 shows the operation of the respective signals.
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Table 1.7.10. Operation of RAS, CASL, CASH, and DW signals
(10) Software wait
A software wait can be inserted by setting the wait control register (address 000816). Figure 1.7.6 shows
wait control register.
You can use the external area i wait bits (where i = 0 to 3) of the wait control register to specify from “No
wait” to “3 waits” for the external memory area. When you select “No wait”, the read cycle is executed in
the BCLK1 cycle. The write cycle is executed in the BCLK2 cycle (which has 1 wait). When accessing
external memory using the multiplex bus, access has two waits regardless of whether you specify “No
wait” or “1 wait” in the appropriate external area i wait bits in the wait control register.
Software waits in the internal memory (internal RAM and internal ROM) can be set using the internal
memory wait bits of the processor mode register 1 (address 000516). Setting the internal memory wait
bit = “0” sets “No wait”. Setting the internal memory wait bit = “1” specifies a wait.
SFR area is accessed with either "1 wait" (BCLK 2-cycle) or "2 waits" (BCLK 3-cycle) by setting the SFR
wait bit (bit 3) of the processor mode register 1 (address 000516). SFR area of CAN must be accessed
with "2 waits".
Table 1.7.11 shows the software waits and bus cycles. Figures 1.7.7 and 1.7.8 show example bus timing
when using software waits.