
Under
development
Preliminary Specifications REV.D
Specifications in this manual are tentative and subject to change.
Mitsubishi Microcomputers
M16C/80 group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Bus Control
38
Item
Status
Oscillation
ON
_____ _____
_____
_______
RD/WR signal, address bus, data bus, CS, BHE
Floating
Programmable I/O ports P0, P1, P2, P3, P4, P5
Maintains status when hold signal is received
P6, P7, P8, P9, P10
P11, P12, P13, P14, P15 (Note)
__________
HLDA
Output “L”
Internal peripheral circuits
ON (but watchdog timer stops)
ALE signal
Undefined
(6) Hold signal
The hold signal is used to transfer the bus privileges from the CPU to the external circuits. Inputting “L” to
__________
the HOLD pin places the microcomputer in the hold state at the end of the current bus access. This status
__________
is maintained and “L” is output from the HLDA pin as long as “L” is input to the HOLD pin. Table 1.7.8
shows the microcomputer status in the hold state. The bus is used in the following descending order of
__________
priority: HOLD, DMAC, CPU.
_____
________
Figure 1.7.5. Example of RD signal extended by RDY signal
__________
HOLD > DMAC > CPU
Table 1.7.8. Microcomputer status in hold state
Item
SFR accessing status
Internal ROM/RAM accessing status
Address bus
Remain address of external area accessed immediately before
Data bus When read
Floating
When write
Floating
_____
______
________
_________
RD, WR, WRL, WRH
Output "H"
________
BHE
Remain external area status accessed immediately before
____
CS
Output "H"
ALE
ALE output
(8) BCLK output
BCLK output can be selected by bit 7 of the processor mode register 0 (address 000416 :PM07) and bit 1
and bit 0 of the system clock select register 0 (address 000616 :CM01, CM00). Setting PM07 to “0” and
CM01 and CM00 to “00” outputs the BCLK signal from P53. However, in single chip mode, BCLK signal
is not output. When setting PM07 to “1”, the function is as set by CM01 and CM00.
Note: Ports P11 to P15 exist in 144-pin version.
(7) External bus status when accessing to internal area
Table 1.7.9 shows external bus status when accessing to internal area
Table 1.7.9. External bus status when accessing to internal area