Advertisement
tus, they can be expanded to 64-byte maximum packet
sizes, which will improve USB throughput. For isochronous
designs, endpoints will need to be converted from end-
point 1 to endpoints 8 through 15.
Feature
EZ-USB Family
Endpoint Pairs
Max. Packet Size
Isochronous (bytes)
Bulk (bytes)
5. Lower power/Easier power management
The Intel 8x930Ax has a 150-mA maximum current spec-
ification under normal operation. The USB specification
requires a device to consume no more than 100 mA during
the initial plug-in. This is because bus-powered hubs can
only supply a maximum of 100 mA per port during bus
enumeration. Following the chip reset, the 8x930Ax oper-
ates in low-clock mode, wherein the CPU and on-chip pe-
ripherals are clocked at a reduced rate until bus enumera-
tion is complete. This reduces the I
100-mA requirement. Thus the Intel 8x930Ax requires the
USB microcontroller to be in idle mode operation during
initial power-on.
Remote wake-up on the 8x930Ax is performed using a
register bit (RWU). Firmware must be used to drive re-
sume signaling on the USB lines. The USB microcontroller
must be awake in order for firmware to be accessed and
generate the remote wake-up operation. However, this
makes it difficult for remote activity peripherals such as
modems and telephones, which are usually in a suspend-
ed state when not in use to save power. An external stim-
ulus, such as a phone call, requires careful timing by the
peripheral designer as it must pull the USB microcontroller
out of suspend operation and write to firmware before ini-
tiating the next series of events. Normally, an external stim-
ulus should trigger a series of events, including the resume
signalling in the host PC right away.
In addition, there is a restriction on the Intel 8x930Ax. If the
8x930Ax is put into power-down mode prior to receiving a
USB Suspend signal from the host, a USB Resume will not
properly wake up the 8x930Ax from the power-down mode.
EZ-USB uses ¼ of the power of the Intel 8x930Ax, making
it ideal for power-sensitive or portable peripherals. As a
result, there is no idle operation mode, since EZ-USB only
has a 50-mA (25-mA typical) maximum current specifica-
tion under the normal operating conditions. If a peripheral
requires between 500 and 600 mA, then the reduction of
100 mA by switching to EZ-USB will allow the peripheral
manufacturer to eliminate the power supply and become a
bus-powered peripheral, thereby saving significant costs.
In addition, EZ-USB resume operation can be performed
with the toggle of an external pin (WAKEUP#), thus mak-
ing it easy for hardware to implement the wake-up opera-
tion. No timing considerations due to waking the USB mi-
crocontroller are necessary.
Converting to EZ-USB requires a 3.3V regulator, as
EZ-USB is powered under 3.3V as opposed to the Intel
8x930Ax which can run off Vbus.
Cypress
Intel
8x930Ax
16
4/6
1024
512/256
64
16/32
to meet the USB
CC
Converting from Intel 8x930Ax to Cypress EZ-USB
Feature
Voltage (volts)
Max. Power (Active)
Max. Current (Active)
6. Smaller board density
The Intel 8x930Ax is housed in a 68 PLCC, which has an
approximate body size of 24 x 24. The EZ-USB family is
packaged in both the 44 PQFP (10 x 10 mm) and 80 PQFP
(14 x 10 mm). The 44 PQFP is useful for applications not
needing the address bus. As a result, a 44 PQFP can use
¼ the board space of the Intel solution.
Feature
Package
Package Board
Density
7. More product options
While the Intel 8x930Ax offers only one product option
which supports both isochronous and bulk, the EZ-USB
family has 10 product options. All the options differ in inter-
nal RAM size, I/O performance, and the support of bulk
only versus isochronous support (see Table 2).
Additional Hardware Issues To Consider When
Converting
8. VID/PID/DID Implementation
With the Intel 8x930Ax, VID/PID/DID information was em-
bodied into the internal ROM or external ROM/EPROM.
If the peripheral designer is implementing the firmware
download feature of EZ-USB, then the VID/PID/DID infor-
mation is housed in a tiny 16-byte (or larger) EEPROM
which is connected through the EZ-USB I
the peripheral designer use an 8K EEPROM to load the
entire firmware through the I
information is contained in the 8K EEPROM. Of course, if
the peripheral designer requires more than 8K of firmware
and uses external memory for firmware, the VID/PID/DID
information is embodied in external memory as with the
8x930Ax.
9. 1.5-k
Pull-up Resistor
The 8x930Ax uses a standard implementation for USB,
attaching a 1.5-k
EZ-USB performs special tricks with the USB signal lines
in performing the ReNumeration operation. As a result, the
1.5-k
resistor is connected directly to our DISCON# pin.
Even if ReNumeration operation is not required, the de-
signer should still connect the 1.5-k
DISCON# pin.
4
Cypress
Intel
EZ-USB Family
8x930Ax
3.0–3.6
4.0–5.25
180 mW
788 mW
50 mA
150 mA
Cypress
Intel
EZ-USB Family
8x930Ax
44 PQFP
68 PLCC
80 PQFP
170 sq. mm
625 sq. mm
432 sq. mm
2
C port. Should
2
C port, then the VID/PID/DID
resistor from D+ to Vbus. However,
resistor to the
Advertisement
