UPD77533 datasheet(47/104 Pages) RENESAS

47 / 104 page

Data Sheet S15671EJ4V0DS

µµµµPD77533

13.2.3 ACK, NACK in case of server command

When the command is a server command, ACK and NACK are used to confirm transmission and reception of

each packet.

If NACK is sent from the host CPU to the

µPD77533, the same packet is re-sent.

The

µPD77533 can send the next packet after receiving ACK from the host CPU.

When a response is output from the

µPD77533 to the host CPU, the host CPU must send either ACK or NACK.

The

µPD77533 stops outputting packets until this ACK or NACK is received.

Figure 13-3. Server Command Flow

14. HARDWARE FLOW CONTROL

In communication between the

µPD77533 and the host CPU, hardware flow control is carried out using CTS-RTS

to prevent the loss of data due to a buffer overflow.

14.1 When Hardware Flow Control Is Not Performed

When hardware flow control is not performed, data may be lost due to a buffer overflow. To prevent this, the host

CPU must execute the following processing.

PD77533

Host CPU

$CA command (CMD-ID = 0x80)

Example of

normal flow

Timeout or error

occurrence

NACK

Example of

abnormal flow

ACK (format 1)

!ca response (CMD-ID = 0x80)

ACK (format 1)

$CA command transmitted

ACK for $CA

!ca response transmitted

ACK for !ca

$CA command (CMD-ID = 0x80)

$CA command transmitted

$CA command (CMD-ID = 0x80)

ACK (format 1)

!ca response (CMD-ID = 0x80)

Timeout or error

occurrence

NACK for $CA

$CA command resent

ACK for $CA

!ca response transmitted

NACK

!ca response (CMD-ID = 0x80)

ACK (format 1)

NACK for !ca

!ca response resent

ACK for !ca

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