AT91SAM7X128 Atmel, AT91SAM7X128 Datasheet - Page 450

• Manufacturer Part Number: AT91SAM7X128
• Description: MCU 32-Bit 91S ARM7TDMI RISC 128KB Flash 1.8V/3.3V 100-Pin LQFP
• Manufacturer: Atmel

Specifications of AT91SAM7X128

• Package: 100LQFP
• Device Core: ARM7TDMI
• Family Name: 91S
• Maximum Speed: 55 MHz
• Ram Size: 32 KB
• Program Memory Size: 128 KB
• Operating Supply Voltage: 1.8|3.3 V
• Data Bus Width: 32 Bit
• Program Memory Type: Flash
• Number Of Programmable I/os: 62
• Interface Type: CAN/Ethernet/SPI/I2S/TWI/USART/USB
• On-chip Adc: 8-chx10-bit
• Operating Temperature: -40 to 85 °C
• Number Of Timers: 3

34.4
34.4.1
34.4.2
450
Typical Connection
AT91SAM7X512/256/128 Preliminary
USB Device Transceiver
VBUS Monitoring
Figure 34-2. Board Schematic to Interface USB Device Peripheral
The USB device transceiver is embedded in the product. A few discrete components are
required as follows:
Pullup enable/disable is done through a MOSFET controlled by a PIO. The pullup is enabled
when the PIO drives a 0. Thus PIO default state to 1 corresponds to a pullup disable. Once the
pullup is enabled, the host will force a device reset 100 ms later. Bus powered devices must
connect the pullup within 100 ms.
VBUS monitoring is required to detect host connection. VBUS monitoring is done using a stan-
dard PIO with internal pullup disabled. When the host is switched off, it should be considered as
a disconnect, the pullup must be disabled in order to prevent powering the host through the pull-
up resistor.
When the host is disconnected and the transceiver is enabled, then DDP and DDM are floating.
This may lead to over consumption. A solution is to connect 330 KΩ pulldowns on DP and DM.
These pulldowns do not alter DDP and DDM signal integrity.
PIO
PIO
DDM
DDP
• the application detects all device states as defined in chapter 9 of the USB specification;
• to reduce power consumption the host is disconnected
• for line termination.
– pullup enable/disable
– VBUS monitoring
5V Bus Monitoring
Pullup Control
0: Enable
1: Disable
47 K
27 K
R
R
EXT
EXT
330 K
330 K
3V3
1.5K
2
3
Connector
6120H–ATARM–17-Feb-09
Type B
1
4