Renesas M16C/6NK Technical Information Seite 74

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Seitenansicht 73
Rev.2.10 Apr 14, 2006 page 50 of 378
REJ09B0124-0210
M16C/6N Group (M16C/6NK, M16C/6NM) 7. Bus
__________
HOLD > DMAC > CPU
__________
7.2.7 HOLD Signal
This signal is used to transfer control of the bus from the CPU or DMAC to an external circuit. When the
__________
input on HOLD pin is pulled low, the MCU is placed in a hold state after the bus access then in process
__________ __________
finishes. The MCU remains in a hold state while the HOLD pin is held low, during which time the HLDA pin
outputs a low-level signal.
Table 7.5 shows the MCU Status in Hold State.
__________
Bus-using priorities are given to HOLD, DMAC, and CPU in order of decreasing precedence (see Figure
7.5 Bus-using Priorities). However, if the CPU is accessing an odd address in word units, the DMAC
cannot gain control of the bus during two separate accesses.
Figure 7.5 Bus-using Priorities
Table 7.5 MCU Status in Hold State
NOTES:
1. When I/O port function is selected.
2. The watchdog timer does not stop when the PM22 bit in the PM2 register is set to 1 (the count source
for the watchdog timer is the on-chip oscillator clock).
3. Ports P11 to P14 are only in the 128-pin veresion.
7.2.8 BCLK Output
If the PM07 bit in the PM0 register is set to 0 (output enable), a clock with the same frequency as that of
the CPU clock is output as BCLK from the BCLK pin. Refer to 8.2 CPU Clock and Peripheral Function
Clock.
Table 7.6 shows the Pin Functions for Each Processor Mode.
Item Status
BCLK Output
_______ _______ ______ _________ _________
A0 to A19, D0 to D15, CS0 to CS3, RD, WRL, WRH, High-impedance
______ ________
WR, BHE
I/O ports P0, P1, P3, P4
(1)
High-impedance
P6 to P14
(3)
Maintains status when hold signal is received
__________
HLDA Output L
Internal peripheral circuits ON (but watchdog timer stops
(2)
)
ALE signal Undefined
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