-8-
Pin No.
Pin Name
I/O
Description
24 ~ 31
32
33
34
35
36
37
38
39
40
41
42
43
44
D0 ~ D7
BKPT
VCC
GND
SDA
SCL
_________
WAKEUP
GND
____
PA4/FWR
____
PA5/FRD
USBD-
USBD+
________
DISCON
VCC
8051 data bus. This bi-directiona bus is high-impedance when inactive, input for bus reads, and
output for bus writes. The data bus is also used to transfer data directly to and from internal EZ-
____
____
USB FIFOS under control of the FRD and FWR strobes. D0-D7 are active only for external bus
accesses, and are driven low in suspend.
Breakpoint. This pin goes active (high) when the 8051 address bus matches the BPADDRH/L
registers and breakpoints are enebled in the USBBAV register (BPEN=1). If the BPPULSE bit in
the USBBAV register is HI, this signal pulses high for eight 24 MHz clocks. If the BPPULSE bit
is LO, the signal remains high until the 8051 clears the BREAK bit (by writing 1 to it) in the
USBBAV register.
3.3V power source
Ground
I
2
C data. Connect to VCC with a 2.2 k resistor.
I
2
C clock. Connect to VCC with a 2.2 k resistor.
USBwakeup. If the 8051is unsuspend, a high to low edge on this pin starts up the oscillator and
interrupts the 8051to allow it to exit the suspend mode.
Ground
Multiplexed pin whose function is selected by the “FWR” (Fast Write) bit of the PORTACFG
register. If FWR=0, the pin is the bi-directional I/O port pin PA4. If FWR = 1 the pin is the write
strobe for an external FIFO.
Multiplexed pin whose function is selected by the “FRD” (Fast Read) bit of the PORTACFG
register. If FRD=0, the pin is the bi-directional I/O port pin PA5. If FRD = 1 the pin is the read
strobe for an external FIFO.
USB D - signal. Connect to the USB D - signal.
USB D+ signal. Connect to the USB D + signal.
Disconnect. This signal drvives low when the 8051 sets the DISCON bit HI (USBCS3). When
________
the DISCON bit is LO, the DISCON pin either drivers high or floats, depending on the state of
the DISCOE bit (USBCS2).
3.3V power source
I/O
O
–
–
O
O
I
–
I/O
I/O
I/O
I/O
O
I
IC DESCRIPTION -1/1 (AN2136SC) -2/2
