M37754 Mitsubishi, M37754 Datasheet - Page 12

• Manufacturer Part Number: M37754
• Description: SINGLE-CHIP 16BIT CMOS MICROCOMPUTER
• Manufacturer: Mitsubishi

Figure 5 shows basic waveforms of the bus interface unit. The RD
signal becomes “L” when the bus interface unit reads an instruction
code or data from memory. The WR signal becomes “L” when the
bus interface unit writes data to memory.
Waveforms (1) and (3) in Figure 5 are used to access a single byte
or two bytes simultaneously. To read or write two bytes simulta-
neously, the first address accessed must be even. Furthermore,
when accessing an external memory area in memory expansion
mode or microprocessor mode, set the bus width select input pin
Fig. 5 Basic waveforms of bus interface unit
12
Internal data bus
Internal data bus
Internal data bus
Internal data bus
Internal address
Internal address
(1)
(3)
(D
(D
(A
(A
(D
(D
0
8
0
8
0
0
– D
– D
– A
– A
– D
– D
WR
WR
bus
bus
RD
RD
23
15
23
15
7
7
)
)
)
)
)
)
___
Address
Address
Data (even)
Data (even)
Data (odd)
Data (odd)
M37754M8C-XXXGP, M37754M8C-XXXHP
Internal data bus
Internal data bus
Internal data bus
Internal data bus
Internal address
Internal address
(2)
(4)
__
(D
(D
(A
(A
(D
(D
8
8
0
0
0
0
– A
– D
– A
– D
– D
– D
WR
bus
WR
bus
RD
RD
23
15
23
15
7
7
)
)
)
)
)
)
(BYTE) to “L” (external data bus width = 16 bits). The internal
memory area is always treated as 16-bit bus width regardless of
BYTE.
When performing 16-bit data read or write, if the conditions for simul-
taneously accessing two bytes are not satisfied, waveforms (2) and
(4) are used to access each byte, one by one.
However, when prefetching the instruction code, if the address of the
instruction code is odd, only one byte is read in the instruction queue
buffer.
M37754S4CGP, M37754S4CHP
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Address (odd)
Address (odd)
MITSUBISHI MICROCOMPUTERS
Invalid data
Invalid data
Data (odd)
Data (odd)
Address (even)
Address (even)
Data (even)
Data (even)
Invalid data
Invalid data