NEC switch - Manual (Page 99)

CHAPTER 8 USB FUNCTION
User’s Manual U12978EJ3V0UD
99
Figure 8-2. Block Diagram of USB Function
Internal bus
Internal bus
USBDP
USBDM
• Handshake packet
• SYNC packet
USB clock
Overflow
INTUSBTM
f
X
INTUSBRD
Start
USB receiver
enable register
(USBMOD)
Data/handshake
packet receive mode
register (URXMOD)
Counter Note 1
Transmit reservation
register (HTXRSV,
DTXRSV)
Transmit/receive pointer
(USBPOB, USBPOW) Remote wakeup
control register
(REMWUP)
EOP generation/detection
Resume & reset
detection control
SYNC detection/
USB clock generator
USB timer Note 4
(7-bit counter)
USB timer start
reservation control
register (USBTCL)
Receive result
store register Note 3
Packet receive status
register (RXSTAT)
CRC
circuit
ENDP
detector
Compare register Note 2
Receive buffer
Transmit buffer
Bit stuff/bit strip
controller
Receive bank
switching ID
detection buffer
NRZI
encoder
Output
latch
Selector
Notes 1. Data/handshake packet receive byte number counter (DRXCON), data packet transmit byte number
counter 0, 1 (DTXCO0, DTXCO1)
2. Token address compare register (ADRCMP), token PID compare register (TIDCMP), data/handshake
PID compare register (DIDCMP)
3. Token packet receive result store register (TRXRSL), data/handshake packet receive result store
register (DRXRSL)
4. See Figure 8-3 for USB timer configuration.