UPD6708 datasheet(36/72 Pages) NEC

36 / 72 page

µPD6708

(2)

Validity of SETSD command

When SETSD command is executed, it remains valid until one of the following cases arises.

• ‘Data read and lock’ (control bits: 3H) or ‘data read’ (control bits: 7H) is received from the master unit.

• ABORT command is executed.

• Power is turned off, or the reset mode is entered.

When the SETSD command is valid, WDB functions as the slave transmit buffer.

Caution The SETSD command can be executed even if the unit is placed in the slave transmission selection halted

state by INIT command.

(3)

Example

When the SETSD command is used to set the number of transmit data bytes to 5, and the transmit data to ABH, CDH,

EFH, 14H, and 25H, the contents of WDB and CMR are as shown below.

Caution Transmit data 14H and 25H should be set when the above command parameters have been read and WDB

is empty.

5.2.7

GETSTA command (command code: 0110)

The GETSTA command is used by a unit to check whether it is locked by another unit.

(1)

Functions

<1> Reads the lock status which indicates whether or not this unit is locked by another unit. ‘1J’ is placed in RDB if the

unit is locked, and ‘0H’ if not locked.

<2> The address (12 bits) of a locked unit is placed in RDB. This data is meaningless when the unit is not locked.

After execution of GETSTA command, the data placed in RDB is as follows.

0000

0101

1010

1011

0100

0101

First Byte

Second Byte

Third Byte

Fourth Byte

WDB

CMR

Second

Data Byte

Third

Data Byte

Number of Transmit

Data Bytes

First

Data Byte

1100

1101

1110

1111

Lock Status

Address of Locked Unit (12 Bits)

First Byte

Second Byte

MSB

LSB

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