
Agere Systems Inc.
165
Data Sheet
July 2001
T8302 Internet Protocol Telephone
Advanced RISC Machine (
ARM
)
13 USB Host Controller
(continued)
Table 146. Hc Control Register
(continued)
Bit #
Key
Reset
R/W
Description
HCD
R/W
HC
R
5
BLE
0b
Bulk list enable.
This bit is set to enable the processing of the
bulk list in the next frame. If cleared by HCD, processing of the
bulk list does not occur after the next SOF. HC checks this bit
whenever it determines to process the list. When disabled, HCD
may modify the list. If
the
Hc bulk current ED register
is point-
ing to an ED to be removed, HCD must advance the pointer by
updating
Hc bulk current ED register
before re-enabling pro-
cessing of the list.
Control list enable. This bit is set to enable the processing of the
control list in the next frame. If cleared by HCD, processing of the
control list does not occur after the next start of frame (SOF). HC
must check this bit whenever it determines to process the list.
When disabled, HCD may modify the list. If the
Hc Control cur-
rent ED register
is pointing to an ED to be removed, HCD must
advance the pointer by updating the
Hc Control current ED reg-
ister
before re-enabling processing of the list.
Isochronous enable. This bit is used by HCD to enable/disable
processing of isochronous EDs. While processing the periodic
list in a frame, HC checks the status of this bit when it finds an
isochronous ED (F = 1). If set (enabled), HC continues process-
ing the EDs. If cleared (disabled), HC halts processing of the
periodic list (that now contains only isochronous EDs) and
begins processing the bulk/control lists. Setting this bit is guaran-
teed to take effect in the next frame (not the current frame).
Periodic list enable. This bit is set to enable the processing of the
periodic list in the next frame. If cleared by HCD, processing of
the periodic list does not occur after the next SOF. HC must
check this bit before it starts processing the list.
Control bulk service ratio. This specifies the service ratio
between control and bulk EDs. Before processing any of the non-
periodic lists, HC must compare the ratio specified with its inter-
nal count to how many nonempty control EDs have been
processed, to determine whether to continue serving another
control ED or switching to bulk EDs. The internal count will be
retained when crossing the frame boundary. In case of reset,
HCD is responsible for restoring this value.
4
CLE
0b
R/W
R
3
IE
0b
R/W
R
2
PLE
0b
R/W
R
1:0
CBSR
00b
R/W
R
CBSR
00
01
10
11
No. of Control EDs Over Bulk EDs Served
1:1
2:1
3:1
4:1