58
Ver 1.4
MITSUBISHI MICROCOMPUTERS
7640 Group
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
The
(USBSOFL)
, shown in Figure 1.59, contains the
lower 8 bits of the 11-bit frame number received from
the host.
The
USB
Frame
Number
, shown in Figure 1.60, contains the up-
per 3 bits of the 11-bit frame number received from
the host.
The
USB Endpoint Index Register (USBINDEX)
,
shown in Figure 1.61, identifies the endpoint pair. It
serves as an index to endpoint-specific IN CSR, OUT
CSR, IN MAXP, OUT MAXP and OUT WRT CNT reg-
isters.
This register also contains two global bits, ISO_UPD
and AUTO_FL, which affect isochronous data trans-
fers for endpoints 1-4.
USB
Frame
Number
Low
Register
High
Register
Fig. 1.59. USB Frame Number Low Register (USBSOFL)
Fig. 1.60. USB Frame Number High Register (USBSOFH)
Fig. 1.61. USB Endpoint Index Register (USBINDEX)
If 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 ISO_UPD = “1” and the ISO
bit of the corresponding endpoint’s IN CSR is set,
then the internal ‘ready to transmit’ signal to the trans-
mit control logic is delayed until the next SOF. In this
way the data loaded in frame n will be transmitted out
in frame n+1. The ISO_UPD bit is a global bit for end-
points 1 to 4, and works with isochronous pipes only.
If AUTO_FL = “1”, ISO_UPD = “1”, and a particular IN
endpoint’s ISO bit is set, then when the USB FCU de-
tects an SOF packet, if the corresponding IN
endpoint’s IN_PKT_RDY = “1”, the USB FCU auto-
matically flushes the oldest packet from the IN FIFO.
In this case, IN_PKT_RDY = “1” indicates that two
data packet are in the IN FIFO. Since, for ISO trans-
fer, double buffering is a requirement; MAXP must set
to be less than or equal to 1/2 of the FIFO size.
ISO_UPD
Reserved
Reserved
Reserved
EPINDX2
EPINDX1
EPINDX0
MSB
7
LSB
0
AUTO_FL
Address: 0058
16
Access: R/W
Reset: 00
16
EPINDX2:0 Endpoint Index:
Bit 2
0 0
0
0
0
1
Others:
Bit 1
Bit 0
0:
1:
0:
1:
0:
Function Endpoint 0
Function Endpoint 1
Function Endpoint 2
Function Endpoint 3
Function Endpoint 4
Undefined
0
1
1
0
Bits 3:5
Reserved (Read/Write "0")
AUTO_FL
AUTO_FLUSH Bit (bit 6)
0: Hardware auto FIFO flush disabled
1: Hardware auto FIFO flush enabled
ISO_UPDATE Bit (Bit 7)
0: ISO_UPDATE disabled
1: ISO_UPDATE enabled
ISO_UPD
FN7
FN5
FN4
FN3
FN2
FN1
FN0
MSB
7
LSB
0
FN6
Address: 0056
16
Access: R
Reset: 00
16
FN7:0
Lower 8 bits of 11-bit frame number issued with a SOF token
Reserved
Reserved
Reserved
Reserved
FN10
FN9
FN8
MSB
7
LSB
0
Reserved
Address: 0057
Access: R
Reset: 00
16
FN10:8
Upper 3 bits of the 11-bit frame number issued with a SOF token
Bits 7:3
Reserved (Read "0")