
Universal Serial Bus Module (USB)
Hub Function I/O Registers
MC68HC908LD64 — Rev. 3.0
Data Sheet
Freescale Semiconductor
Universal Serial Bus Module (USB)
195
software is responsible to propagate the traffic between the root port
and the enabled downstream port by setting the RESUMx control bit.
Reset clears this bit.
EOF2 is generated by the MCU every millisecond, if SOF is not
detected when three or more EOF2 have occurred, software can set
the SUSPND bit and put the MCU into suspend mode.
D0+, D0– — Root Port Differential Data
These read-only bits are the differential data shown on the hub root
ports. When the SUSPND bit is 0, the data is the latched state at the
last EOF2 sample point. When the SUSPND bit is 1, the data reflects
the current state on the data line while accessing this register.
14.6.2 USB Hub Downstream Port Control Registers (HDP1CR–HDP4CR)
PENx — Downstream Port Enable Control Bit
This read/write bit determines whether the enabled or disabled state
should be assigned to the downstream port. Setting this bit to 1
enables the port; clearing this bit to 0 disables the port. In the enabled
state a full-speed port propagates all downstream signaling;
Address:
$0051–$0054
HRP1CR–HRP4CR
Bit 7
654321
Bit 0
Read:
PEN1
LOWSP1
RST1
RESUM1
SUSP1
0D1+
D1–
Write:
Read:
PEN2
LOWSP2
RST2
RESUM2
SUSP2
0D2+
D2–
Write:
Read:
PEN3
LOWSP3
RST3
RESUM3
SUSP3
0D3+
D3–
Write:
Read:
PEN4
LOWSP4
RST4
RESUM4
SUSP4
0D4+
D4–
Write:
Reset:
000000
X
X = Indeterminate
= Unimplemented
Figure 14-4. USB Hub Downstream Port Control Registers
(HDP1CR–HDP4CR)