UPD6708 datasheet(34/72 Pages) NEC

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µPD6708

5.2.4

MREQ2 command (command code: 0011)

(1)

Functions

This command re-executes a master communication (transmission or reception). If master transmission or reception

stops midway, the master communication is re-executed from the stopped condition.

(2)

Command execution conditions

If a communication control command other than an MREQ2 command is executed after the master communication ends

midway, the MREQ1 command may not re-execute the communication correctly from the communication interrupted

condition.

(3)

Example

When re-execution is performed by the MREQ2 command when communication has been interrupted due to generation

of a timing error after transmission of two bytes (12H and 34H) in mode 1, as in the MREQ1 command example, the contents

of WDB and CMR are as shown below.

The previously set MREQ1 command values are used for the broadcast bits, control bits and number of transmit data

bytes.

Cautions

1. A master communication performed by execution of the MREQ1 and MREQ2 commands is performed

in only one frame. However, if the unit loses in arbitration, the frame is automatically reset up twice

(three times in total).

2. INIT command must be executed before setting the MREQ1 or MREQ2 command. If MREQ1 or MREQ2

is set before execution of INIT command, master communication will not be performed.

5.2.5

ABORT command (command code: 0100)

(1)

Functions

This command aborts master communications and slave unit data transmissions.

<1> It clears the data placed in WDB.

<2> It cancels the slave transmit data (SETSD command).

(2)

Example

When the master unit begins communication as in the MREQ1 command example, a communication error is generated

and the two bytes of transmit data (12H and 34H) remaining in WDB are canceled by ABORT command, the contents of

CMR are as shown below.

0101

0110

0111

1000

0100

0011

First Byte

Second Byte

Data to be Transmitted upon

Re-Execution of Command

Third Byte

Fourth Byte

WDB

CMR

UPD6708 数据表(PDF) 34 Page - NEC

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