
162
Agere Systems Inc.
T8302 Internet Protocol Telephone
Advanced RISC Machine (
ARM
)
Data Sheet
July 2001
13 USB Host Controller
(continued)
5-5595 (F)a.
Figure 21. USB Block Diagram
13.2 USB Registers
The host controller (HC) contains a set of on-chip operational registers that are mapped into a noncachable portion
of the system-addressable space. These registers are used by the host controller driver (HCD). According to the
function of these registers, they are divided into four partitions, specifically for control and status, memory pointer,
frame counter, and root hub. All of the registers should be read and written as 32-bit words.
The OpenHCI specification may allocate reserve bits. To ensure interoperability, the host controller driver that does
not use a reserved field should not assume that the reserved field contains a 0. Furthermore, the host controller
driver should always preserve the value(s) of the reserved field(s). When an R/W register is modified, the host con-
troller driver should first read the register, modify the bits desired, then write the register with the reserved bits still
containing the read value. Alternatively, the host controller driver can maintain an in-memory copy of previously
written values that can be modified and then written to the
host controller register
. When a write to
set/clear reg-
ister
is written, bits written to reserved fields should be 0.
ADDRESS
H
DATA
DATA
CONTROL
HCI
SLAVE
BLOCK
OHCI
REGs
DATA
ADDRESS/
DATA
CONTROL
HCI
MASTER
BLOCK
FIFO STATUS
DATA
DATA
TX
64 x 8
CFIFO
DATA
DATA
DPLL
HSIE
S/M
MUX
12/1.5
ROOT
HUB
AND
SIE
PROLIST
BLOCK
ED & TD
REGs
CONTROL
CONTROL
USB
CSTATE
DATA
CONTROL
RX
TX
USB
USB
USB
S/M
HUB
REGs
S/M
S/M
HUB
BLOCK
CONTROL
CONTROL
D
A
D
DATA
STATUS
STATUS
U
X
C
V
R
U
X
C
V
R
U
X
C
V
R
OHC (USB OpenHCI HOST CONTROLLER)
HCI BUS
INTERFACE
USB
INTERFACE
ADDRESS
DATA
DATA
APB REGISTER INTERFACE
ARM
APB I/F
TX FIFO
ADDRESS
RX
RX FIFO
CONTROL
ASB
MASTER
S/M
ARM
ASB I/F
FIFO
64 x 8