enCoRe™ V CY7C643xx, enCoRe™ V LV CY7C604xx TRM, Document No. 001-32519 Rev *H
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Full-Speed USB
20.3.14 USB_CR1 Register
The USB Control Register 1 (USB_CR1) is used to config-
ure the internal regulator and the oscillator tuning capability.
Bit 2: BusActivity.
The BusActivity bit is a “sticky” bit that
detects any non-idle USB event that has occurred on the
USB bus. After set to high by the SIE to indicate the bus
activity, this bit retains its logical high value until firmware
clears it. Writing a '0' to this bit clears it; writing a '1' pre-
serves its value. ‘0’ is no activity. '1' is non-idle activity (D+ =
low) was detected since the last time the bit was cleared.
Bit 1: EnableLock.
Set this bit to turn on the automatic fre-
quency locking of the internal oscillator to USB traffic.
Unless an external clock is being provided, this bit must
remain set for proper USB operation. ‘0’ is locking disabled.
'1' is locking enabled.
Bit 0: RegEnable.
This bit controls the operation of the
internal USB regulator. For applications with device supply
voltages in the 5-V range, set this bit high to enable the
internal regulator. For device supply voltages in the 3.3-V
range, clear this bit to connect the transceiver directly to the
supply. ‘0’ is passthrough mode. Use for Vdd = 3.3-V range.
'1' is regulating mode. Use for Vdd = 5-V range.
For additional information, refer to the
20.3.15 USB_MISC_CR Register
The USB Miscellaneous Control Register controls the clocks
to the USB block, to make the IMO work with better accu-
racy for the USB part and to disable the single-ended input
of the USBIO in the case of a non-USB part.
Bit 2: USB_SE_EN.
The single-ended outputs of USBIO is
enabled or disabled based upon this bit setting. Set this bit
to '1' when using this part as a USB part for USB transac-
tions to occur. Set this bit to '0' to disable single-ended out-
puts of USBIO. The DPO and DMO are held at logic high
state and RSE0 is held at a low state.
Note
Bit [1:0] of the USBIO_CR1 register is also affected
depending on this register setting. When this bit is '0'
(default), regardless of the DP and DM state, the DPO and
DMO bits of USBIO_CR1 are '11b'.
Bit 1: USB_ON.
This bit is used by the IMO DAC block to
either work with better DNL consuming higher power, or with
sacrificed DNL consuming lower power. Set this bit to '1'
when the part is used as a USB part. A '0' runs the IMO with
sacrificed DNL by consuming less power. A '1' runs the IMO
with better DNL by consuming more power.
Bit 0: USB_CLK_ON.
This bit either enables or disables
the clocks to the USB block. It is used to save power in
cases when the device need not respond to USB traffic. Set
this bit to '1' when the device is used as a USB part.
When this bit is a ‘0’, all clocks to the USB block are driven.
The device does not respond to USB traffic and none of the
USB
registers,
except
IMO_TR,
IMO_TR1,
and
USBIO_CR1, listed in the
Register Definitions on page 147
are writable.
When this bit is a ‘1’, clocks are not blocked to the USB
block. The device responds to USB traffic depending on the
other register settings mentioned under
in the
Full-Speed USB chapter on page 141
For additional information, refer to the
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Access
1,30h
BusActivity
EnableLock
RegEnable
# : 0
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Access
1,BDh
USB_SE_EN
USB_ON
USB_CLK_ON
RW : 0