7702 Datasheet, PDF (282/522 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER

CONNECTION WITH EXTERNAL DEVICES
12.4 Hold function
12.4 Hold function
When composing the external circuit (DMA) which accesses the bus without using the central processing
unit (CPU), the Hold function is used to generate a timing for transferring the right to use the bus from the
CPU to the external circuit. Fix bit 0 of the port P4 direction register to “0.”
In the memory expansion or microprocessor mode, the microcomputer enters Hold state by input of “L” level
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to the HOLD pin and retains this state while the level of the HOLD pin is at “L.” Table 12.4.1 lists the
microcomputer’s state in Hold state.
In Hold state, the oscillation of the oscillator does not stop. Accordingly, the internal peripheral devices can
operate. However, Watchdog timer stops operating.
Table 12.4.1 Microcomputer’s state in Hold state
Item
State
Oscillation
Operating
φ
Operating
φCPU
Stopped at “L”
_
E
Stopped at “H”
Pins A0 to A7, A8/D8 to A15/D15,
__ ___
A16/D0 to A23/D7, R/W, BHE
_____
Pins HLDA (Note 1), ALE
Floating
Outputs “L” level.
Pin P42/φ1
In the memory expansion mode:
•When clock φ1 output select bit^U = “1,” this pin outputs clock φ1.
•When clock φ1 output select bit = “0,” this pin retains the state when Hold
request was accepted.
In the microprocessor mode:
•This pin outputs clock φ1.
Pins P43 to P47, P5 to P8 (Note 2) Retains the state when Hold request was accepted.
Watchdog timer
Stopped
Clock φ1 output select bit^U : Bit 7 at address 5E_{__}16_{___}
Notes 1: The 7703 Group does not have the HLDA pin.
2: When this functions as a programmable I/O port.
12–16
7702/7703 Group User’s Manual