UPD77533 datasheet(22/104 Pages) RENESAS

22 / 104 page

Data Sheet S15671EJ4V0DS

µµµµPD77533

4.1.2 When command from host CPU is local command

When the command is a local command, packet transmission/reception is not confirmed using ACK and NACK. A

response to the command (command execution result) is used as the “ACK” from the

µPD77533 to the host CPU.

There is no equivalent to ACK for commands that receive no response (baud rate change command).

If an error occurs during an uplink (see Figure 4-3), even if the host CPU sends NACK to the

µPD77533, the

µPD77533 will perform no processing. The host CPU must therefore re-send the same packet without returning

NACK.

If an error occurs during a downlink (see Figure 4-4), the

µPD77533 sends the host CPU the Error Status

command (CMD-ID: 0x3F). Once the host CPU receives the Error Status command (CMD-ID: 0x3F), the host CPU

must re-send the same packet to the

µPD77533.

Figure 4-3. Command Error Control Flow for Local Commands (Uplink Error)

Figure 4-4. Command Error Control Flow for Local Commands (Downlink Error)

4.2

Timeout Error (Command Packet Interruption)

A timeout occurs in the

µPD77533 if the specified time elapses after the last data of a packet is received while

packet reception is not complete.

When a timeout occurs, the

µPD77533 returns a timeout “Error Status” (CMD-ID: 0x3F), and all packet data

received up to that point is discarded.

PD77533

Host CPU

Command error detected

(Local command)

Response sent

Previous response

re-sent

(Local command)

Previous local

command re-sent

PD77533

Host CPU

(Local command)

Previous command

re-sent

NACK ("Error Status" (0x3F))

(Local command)

Command error detected

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