Renesas M16C Series User Manual page 70

M30240 Group
1.2.18.4.7 USB Frame Number Registers
The USB Frame Number Low Register, shown in Figure 1.38, contains the lower 8 bits of the 11-bit frame
number received from the host. The USB Frame Number High Register, shown in Figure 1.39 contains the
upper 3 bits of the 11-bit frame number received from the host.
USB Frame Number Low Register
b7 b6 b5 b4
Figure 1.38: USB Frame Number Low Register
USB Frame Number High Register
b7 b6 b5 b4
0 0 0 0 0
Figure 1.39: USB Frame Number High Register
1.2.18.4.8 USB ISO Control Register
The USB ISO Control Register, shown in Figure 1.40, contains two global bits, ISO_UPD and AUTO_FL for
controlling endpoints 1-4 isochronous data transfer.
When ISO_UPD = "0", a data packet in an endpoint's IN FIFO is always 'ready to transmit' upon receiving the
next IN_TOKEN from the host (with matched address and endpoint number) if the endpoint's IN_PKT_RDY
is set.
When ISO_UPD = "1" and the ISO/TOGGLE_INIT bit of the corresponding endpoint's IN CSR is set, the in-
ternal 'ready to transmit' signal to the transmit control logic is not activated when the endpoint's IN_PKT_RDY
is set. Instead, it is activated when the next SOF is received, this way, the data loaded in frame n is transmitted
out in frame n+1. The ISO_UPD bit is a global bit for endpoints 1-4 and works with isochronous pipes only.
When AUTO_FL = "1", ISO_UPD = "1", a particular IN endpoint's ISO/TOGGLE_INIT bit is set, and the IN
endpoint's IN_PKT_RDY = "1", the USB FCU detects a SOF packet and the USB FCU automatically flushes
the oldest packet from the IN FIFO. In this case, IN_PKT_RDY = "1", indicates that two data packets are in
the IN FIFO. Because double buffering is a requirement for ISO transfer, MAXP must be set to less than or
equal to 1/2 of the FIFO size.
USB ISO Control Register
b7 b6 b5 b4
0 0 0 0 0 0
Figure 1.40: USB ISO Control Register
Rev.1.00 Sep 24, 2003 Page 52 of 360
b3 b2 b1 b0
Symbol
USBSOFL
Bit symbol
Lower 8 bits of the 11-bit
FN0 to FN7
frame number issued with a
SOF token
b3 b2 b1 b0
Symbol
USBSOFH
Bit symbol
FN8
Upper 3 bits of the 11-bit
frame number issued with a
FN9
SOF token
FN10
Reserved
b3 b2 b1 b0
Symbol
USBISOC
Bit name
Bit symbol
Reserved
AUTO_FLUSH Bit
AUTO_FL
ISO_UPDATE Bit
ISO_UPD
Address
0306
16
Bit name Function
Address
0307
16
Bit name Function
Must always be set to "0"
Address
0308
16
Must always be set to "0"
0 : Hardware auto FIFO flush diabled
1 : Hardware auto FIFO flush enabled
0 : ISO_UPDATE disabled
1 : ISO_UPDATE enabled
Universal Serial Bus
When reset
00
16
R W
X
When reset
00
16
R W
X
X
When reset
00
16
Function R W