
Mitsubishi microcomputers
M16C / 62 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Bus Control
37
Table 1.12.6. Microcomputer status in hold state
Item
Status
Oscillation
R/W signal, address bus, data bus, CS, BHE
Programmable I/O ports
ON
Floating
Floating
Maintains status when hold signal is received
Output “L”
ON (but watchdog timer stops)
Undefined
P0, P1, P2, P3, P4, P5
P6, P7, P8, P9, P10
HLDA
Internal peripheral circuits
ALE signal
__________
HOLD > DMAC > CPU
(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 1.12.6
shows the microcomputer status in the hold state.
Bus-using priorities are given to HOLD, DMAC, and CPU in order of decreasing precedence.
Figure 1.12.4. Bus-using priorities
(7) External bus status when the internal area is accessed
Table 1.12.7 shows the external bus status when the internal area is accessed.
Table 1.12.7. External bus status when the internal area is accessed
Item
SFR accessed
Internal ROM/RAM accessed
Address bus
Address output
Maintain status before accessed
address of external area
Data bus
When read
Floating
Floating
When write
Output data
Undefined
RD, WR, WRL, WRH
RD, WR, WRL, WRH output
Output "H"
BHE
BHE output
Maintain status before accessed
status of external area
CS
Output "H"
Output "H"
ALE
Output "L"
Output "L"