Universal Serial Bus (USB)
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
31-3
Figure 31-1. USB Interface
The reference clock for the USB controller (USBCLK) is used by the DPLL circuitry to recover the bit
rate clock. The source for USBCLK is selected in SICR, see
Section 20.2.4.3, “SI Clock Route Register
(SICR).”
The MPC885 can run at different frequencies, but the USB reference clock must be four times
the USB bit rate. Thus, USBCLK must be 48 MHz for a 12-Mbps full speed transfer or 6 MHz for a
1.5-Mbps low-speed transfer.
There are six I/O pins associated with the USB port. Their functionality is described in
Table 31-1
.
Additional control lines that might be needed by some transceivers (e.g. speed select, low power control)
may be supported by general purpose output lines.
Table 31-1. USB Pins Functions
Signal
I/O
Function
USBTXN,
USBTXP
O
Outputs from the USB transmitter, inputs to the differential driver.
.
USBOE
O
Output enable. Enables the transceiver to send data on the bus.
USBTXP
USBRXD
D+
D-
USBOE
USBTXN
USBRXP
USBRXN
MPC885
+
–
USB
transceiver
TP
TN
Result
0
0
single ended “0”
0 1
logic
“0”
1
0
logic “1”
1
1
—
Summary of Contents for PowerQUICC MPC870
Page 98: ...MPC885 PowerQUICC Family Reference Manual Rev 2 I 4 Freescale Semiconductor ...
Page 118: ...MPC885 Overview MPC885 PowerQUICC Family Reference Manual Rev 2 1 20 Freescale Semiconductor ...
Page 158: ...The MPC8xx Core MPC885 PowerQUICC Family Reference Manual Rev 2 3 18 Freescale Semiconductor ...
Page 288: ...MPC885 PowerQUICC Family Reference Manual Rev 2 III 4 Freescale Semiconductor ...
Page 554: ...MPC885 PowerQUICC Family Reference Manual Rev 2 V 6 Freescale Semiconductor ...
Page 1090: ...UTOPIA Interface MPC885 PowerQUICC Family Reference Manual Rev 2 43 8 Freescale Semiconductor ...
Page 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
Page 1336: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 16 Freescale Semiconductor ...
Page 1358: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 38 Freescale Semiconductor ...
Page 1370: ...MPC880 MPC885 PowerQUICC Family Reference Manual Rev 2 E 4 Freescale Semiconductor ...
Page 1386: ...Revision History MPC885 PowerQUICC Family Reference Manual Rev 2 I 2 Freescale Semiconductor ...