7641_06 Datasheet, PDF (314/385 Pages) Renesas Technology Corp – 8-BIT SINGLE-CHIP MICROCOMPUTER

7641 Group
APPENDIX
3.3 Notes on use
•Use the transfer instructions such as LDA and STA to set the registers: USB interrupt status
registers 1, 2 (addresses 005216, 005316); USB endpoint 0 IN control register (address 005916); USB
endpoint x IN control register (address 005916); USB endpoint x OUT control register (address
005A16). Do not use the read-modify-write instructions such as the SEB or the CLB instruction.
When writing to bits shown by Table 32 using the transfer instruction such as LDA or STA, a value
which never affect its bit state is required. Take the following sequence to change these bits
contents:
(1) Store the register contents onto a variable or a data register.
(2) Change the target bit on the variable or the data register. Simultaneously mask the bit so that
its bit state cannot be changed. (See to Table 3.3.1.)
(3) Write the value from the variable or the data register to the register using the transfer instruction
such as LDA or STA.
•To use the AUTO_SET function for an IN transfer when the AUTO_SET bit is set to 1, set the FIFO
to single buffer mode.
Table 3.3.1 Bits of which state might be changed owing to software write
Register name
USB endpoint 0 IN control register
USB endpoint x (x = 1 to 4) IN control register
USB endpoint x (x = 1 to 4) OUT control register
Bit name
IN_PKT_RDY (b1)
DATA_END (b3)
FORCE_STALL (b4)
IN_PKT_RDY (b0)
UNDER_RUN (b1)
OUT_PKT_RDY (b0)
OVER_RUN (b1)
FORCE_STALL (b4)
DATA_ERR (b5)
Value not affecting state (Note)
“0”
“0”
“1”
“0”
“1”
“1”
“1”
“1”
“1”
Note: Writing this value will not change the bit state, because this value cannot be written to the bit by software.
(6) Others
•When the USB SOF Port Select Bit is “1”, the reference pulse of 83.3 ns (φ = 12 MHz) is output
from the P70/SOF pin and synchronized with the SOF packet.
Rev.2.00 Aug 28, 2006 page 35 of 108
REJ09B0336-0200