C540U
C541U
Table 2
Pin Definitions and Functions (cont’d)
Symbol
Pin Numbers
I/O*) Function
P-LCC-44 P-SDIP-52
P0.0 - P0.7 44 - 36 50 - 43
I/O Port 0
is an 8-bit open-drain bidirectional I/O port. Port 0
pins that have 1's written to them float, and in that
state can be used as high-impedance inputs. Port 0
is also the multiplexed low-order address and data
bus during accesses to external program and data
memory. In this application it uses strong internal
pullup resistors when issuing 1's.
VCCU
1
1
– Supply voltage
for the on-chip USB transceiver circuitry.
VSSU
2
2
– Ground (0V)
for the on-chip USB transceiver circuitry.
VCC
8, 23
10, 26
– Supply voltage
for ports and internal logic circuitry during normal,
idle, and power down mode.
VSS
9, 22
11, 25
– Ground (0V)
for ports and internal logic circuitry during normal,
idle, and power down mode.
*) I = Input
O = Output
Semiconductor Group
11
1997-10-01