UPD6708 datasheet(45/72 Pages) NEC

45 / 72 page

µPD6708

Table 7-2. Timing for Reading Transmit Data from WDB

(The minimum time after transmission start return code (0H) is set)

Transmit Data

Timing for Reading Transmit Data from WDB (

µs)

Mode 0

Mode 1

Mode 2

Transmit data (first byte)

Approx. 1580

Approx. 400

Approx. 290

Transmit data (second byte)

Approx. 3160

Approx. 800

Approx. 580

:::

Transmit data (N-th byte)

Approx. 1580

× N

Approx. 400

× N

Approx. 290

× N

7.2.2

Transmitting slave status address and lock address

When the

µPD6708 receives 0H, 4H, 5H, and 6H as control bits from the master unit, the slave status and lock address

are generated automatically and sent to the master unit. As a result, there is no necessity for the host controller to be involved

in the transmission of the slave status and lock address.

7.3

Master Reception

When a unit becomes a master unit by setting 0H, 3H, 4H, 5H, 6H, and 7H as control bits and executing the MREQ1

or MREQ2 command, and receives data, slave status and lock address from the slave unit, the following will occur.

(1)

When the master unit returns an acknowledge in the message length field, the slave address, control bits and message

length bits are placed in the read data buffer (RDB) by the MREQ1 command as shown in Figure 7-4, the “master reception

start” return code (6H) is placed in STR, and an interrupt request is generated.

Figure 7-4. Data Exchange During Master Reception (Contents of RDB)

(2)

Each time one byte of receive data is received, it is placed in RDB.

(3)

Each time 20 bytes (RDB capacity) of receive data are received, if RDB is full, a “master receive buffer full” return code

(5H) is placed in STR, and an interrupt request is generated.

(4)

After one frame of data is placed in RDB, a “master reception normal termination” return code (6H) is placed in STR

and an interrupt request is generated.

(5)

If a communication error occurs during reception and communication stops without receiving all of the data transmitted

from the slave unit, a “termination during master reception” return code (7H) is placed in STR and an interrupt request

is generated.

The areas where

µPD6708 places receive data, etc., in RDB are shown below.

Slave Address (12 Bits)

First Byte

Second Byte

Third Byte

Fourth Byte Onward

RDB

Message Length Bits

Control Bits

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