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NEC switch User Manual

Page 113

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CHAPTER 8 USB FUNCTION

User’s Manual U12978EJ3V0UD

113

Table 8-2 shows the state of each flag after receiving the USB reset signal and the Resume signal during the

bus idle state and bus suspend state.

Table 8-2. Flag of RXSTAT After Reception of USB Reset Signal and Resume Signal

Bus State

Device State

Received Signal

RESMRX

SE0RX

URESRX

USB reset

0

1

1

Idle

Main system clock

operation mode

Resume

1

1

0

USB reset

0

1

1

Suspend

STOP mode

Resume

1

1

0

(4) Data/handshake packet receive result store register (DRXRSL)

This register stores the data/handshake packet reception result.

Register contents are updated upon reception of data/handshake EOP.

DRXRSL is set with a 1-bit or 8-bit memory manipulation instruction.

RESET input sets DRXRSL to 00H.

Figure 8-13. Format of Data/Handshake Packet Receive Result Store Register

Symbol

<6>

<7>

<5>

4

3

2

<1>

0

CR16ER DBITER

DBYER

0

0

0

DIDRST

0

CR16ER

CRC error detection (16-bit mode)

0

1

FF65H

Address

DRXRSL

After reset

00H

R/W

R/W

CRC error did not occur in received data packet.

CRC error occurred in received data packet.

DBITER

Bit stuffing error detection

0

1

Bit stuffing error did not occur in received data/handshake packet.

Bit stuffing error occurred in received data/handshake packet.

DBYER

Received data/handshake packet length error detection

0

1

Packet length of received data/handshake packet is normal.

Packet length of received data/handshake packet is abnormal.

DIDRST

Data/handshake packet ID comparison result

0

1

Received data/handshake packet ID and value of data/handshake PID compare register (DIDCMP)
do not match.

Received data/handshake packet ID and value of DIDCMP match.

(5) Token packet receive result store register (TRXRSL)

This register stores the token packet reception status.

Register contents are updated upon reception of token packet EOP.

TRXRSL is set with a 1-bit or 8-bit memory manipulation instruction.

RESET input sets TRXRSL to 00H.