NEC switch - Manual (Page 106)

CHAPTER 8 USB FUNCTION
User’s Manual U12978EJ3V0UD
106
(6) Data/handshake packet receive byte number counter (DRXCON)
This register sets the number of data of the data/handshake packet to be received. During data/handshake
packet reception, if this register value and the transmit/receive pointer (USBPOW) value match, a match signal
is output from the comparator.
During data packet reception, set the USBPOW address at which the last byte before the appended CRC
redundant bits is stored to DRXCON. When a handshake packet is received, set DRXCON to 10H.
DRXCON is set with an 8-bit memory manipulation instruction.
RESET input sets DRXCON to 18H.
SETUP reception Note also sets DRXCON to 18H.
Note SETUP reception implies the satisfaction of all the following three conditions.
• Matching of address
• Endpoint 0 received
• No error in reception
(7) Data packet transmit byte number counters 0 and 1 (DTXCO0 and DTXCO1)
DTXCO0 sets the data packet data number of transmit data bank 0 and DTXCO1 sets the transmit data number
of transmit data bank 1. During data packet transmission, if these register values and the transmit/receive
pointer (USBPOW) value match, a match signal is output from the comparator.
The value to be set to these registers is the USBPOW address (buffer 0: 20H to 28H, buffer 1: 30H to 38H) at
which the last byte before the appended CRC redundant bits is stored.
DTXCO0 and DTXCO1 are set with an 8-bit memory manipulation instruction.
RESET input sets DTXCO0 to 20H and DTXCO1 to 30H.
(8) Token PID compare register (TIDCMP)
This register sets the token packet ID to be received. If this register value and the value of the receive token
PID (USBRTP) match during token packet reception match, TIDRST (bit 1 of the token packet receive result
store register (TRXRSL)) is set.
TIDCMP is set with an 8-bit memory manipulation instruction.
RESET input sets TIDCMP to 00H.