UPD6708 datasheet(28/72 Pages) NEC

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µPD6708

4.3

Reset Mode

When the RESET pin is driven low, the

µPD6708 enters the reset mode. To release the reset mode, the RESET pin

must be driven high and a reset release command input.

There are two methods of resetting the

µPD6708, as follows.

(1)

Resetting with RESET pin

If the RESET pin is driven low, the

µPD6708 will enter the reset mode.

To exit the reset mode, drive the RESET pin high and set bit 7 of CMR to ‘0’.

(2)

Resetting by software

If bit 7 of CMR is set to ‘1’ with the RESET pin fixed high, the

µPD6708 will enter the reset mode.

To exit the reset mode, set bit 7 to ‘0’.

When powering on, the RESET pin must be driven low to execute a reset.

The

µPD6708 will be in the following condition directly after leaving the reset mode.

<1> IEBus slave status is intialized.

Table 4-6. Slave Status Values after Leaving Reset Mode

Bit

Value

Meaning

Bit 7

Up to mode 2 is supported

Bit 6

Bit 5

Always ‘0’

Bit 4

The slave transmission section has stopped.

Bit 3

Always ‘0’

Bit 2

Unit is not locked.

Bit 1

Slave receive buffer is empty.

Bit 0

Slave transmit buffer is empty.

<2> WDB and RDB are empty.

<3> Reception is disabled.

Slave reception and broadcast reception are not acknowledged.

UPD6708 Datasheet(PDF) 28 Page - NEC

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