UPD77112GC データシートの表示（PDF） - NEC => Renesas Technology

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UPD77112GC

16-BIT FIXED-POINT DIGITAL SIGNAL PROCESSORS

NEC => Renesas Technology 

µPD77110, 77111, 77112

4.2 Initializing PLL

Initializing the PLL starts from the 1024th input clock after the RESET pin has been asserted active (low level).

Initialization takes 1024 clocks and it takes the PLL 100 µs to be locked.

After that, the DSP operates with the set value of the PLL specified by a mask option (µPD77111 or 77112) or an

external pin (µPD77110) when the RESET pin is deasserted inactive (high level).

After initializing the PLL, be sure to execute boot-up processing to re-initialize the internal RAM. To initialize the

PLL, the internal memory contents and register status of the DSP are not retained.

If the RESET pin is deasserted inactive before the PLL initialization mode is set, the DSP is normally reset (the

PLL is not initialized).

CLKIN

RESET

PLL initialization

(internal status)

1

1024

2048

Approx. 100 µs

PLL lock time

PLL initialization

mode

Caution Do not deassert the RESET signal inactive in the PLL initialization mode and during PLL lock

period.

5. FUNCTIONS OF BOOT-UP ROM

To rewrite the contents of the instruction memory on power application or from program, boot up the instruction

RAM by using the internal boot-up ROM.

The µPD77110 has a function to verify the contents of the internal instruction RAM in the boot-up ROM.

5.1 Boot at Reset

After hardware reset has been cleared, the boot program first reads the general-purpose I/O ports P0 and P1 and,

depending on their bit pattern, determines the boot mode (self boot or host boot). After boot processing, processing

is executed starting from the instruction at address 0x200 (reset entry) of the instruction memory.

The pins (P0 and P1) that specify the boot mode must be kept stable for the duration of 3 clocks before and for

the duration of 12 clocks after reset has been cleared (the clock is input from CLKIN).

P1

P0

Boot Mode

0

0

Does not execute boot but branches to address 0x200Note.

0

1

Executes host boot and then branches to address 0x200.

1

1

Executes self boot and then branches to address 0x200.

1

0

Setting prohibited

Note This setting is used when the DSP must be reset to recover from the standby mode after reset boot has

been executed once.

24

Data Sheet U12801EJ4V0DS00

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