UPD6708 datasheet(16/72 Pages) NEC

16 / 72 page

µPD6708

2.4

Transfer Data (Contents of Data Field)

The contents of the data field are data specified by the control bits.

Table 2-3. Functions of Control Bits

Bit 3 Note 1

Bit 2

Bit 1

Bit 0

Function Note 2

Reads slave status (SSR)

Undefined

Reads and locks data

Reads lock address (lower 8 bits)

Reads lock address (higher 4 bits)

Reads and unlocks slave status (SSR)

Reads data

Undefined

Writes and locks command

Writes and locks data

Undefined

Writes command

Writes data

Notes 1.

Depending on the value of bit 3 (MSB), the transfer direction of the message length bits of the subsequent

message field and data field differs.

When bit 3 is “1”, data are transferred from the master unit to the slave unit.

When bit 3 is “1”, data are transferred from the slave unit to the master unit.

3H, 6H, AH, and BH are control bits that specify locking or unlocking.

If any of undefined values 1H, 2H, 8H, 9H, CH, or DH is transmitted, no acknowledge bit is returned.

A unit locked by the master unit rejects acknowledging the control bits and does not output the acknowledge bit if the

control bits received from the master unit which requested locking is in any other state than that shown in Table 2-4.

Table 2-4. Control Field Corresponding to Locked Slave Unit

Bit 3

Bit 2

Bit 1

Bit 0

Function

Reads slave status

Reads lock address (lower 8 bits)

Reads lock address (higher 4 bits)

UPD6708 Datasheet(PDF) 16 Page - NEC