Preliminary - Information Subject to Change - 9/24/98
EZ-USB Development Board
5 - 19
Table 5-12: Expansion Connectors Signal Descriptions
Signal
Type
Description
Power Signals
GND
PWR
Signal Ground. Connected to proto board ground plane.
3.3V
PWR
3.3 volts from the EZDB Regulator U6
5V
PWR
5 volts supplied from either of two sources, depending on the position of the
shorting plug on EZDB J4 (Power Select). If pins 2-3 are jumpered (“BUS”), the
power is supplied from pin 1 of the USB connector. If pins 1-2 are jumpered
(“EXT”) the power is supplied externally from J2 (“EXT 5V). The red “PWR” LED
is connected to this signal. NOTE: USB supplies 100 ma max (hub) or 500 ma max
(direct), and can be as low as 4.4V due to cable and connector drops.
NC
Unconnected on the EZDB.
8051 Interface Signals
A[15..0]
OUT
8051 Address Bus. Always drives.
D[7..0]
IO
8051 Bi-directional Data Bus. Also carries the data for fast transfers (using FRD#/
FWR strobe signals). Drives low in suspend.
PSEN#
OUT
8051 Program Store Enable strobe
RD#
OUT
8051 external memory Read strobe
WR#
OUT
8051 external memory Write strobe
Programmable Control Signals (from EZDB U5, a 22V10) See page 5-15 for equations.
CE1#
OUT
Chip enable signal for EZDB U1, a 32Kbyte RAM
CE2#
OUT
Chip enable signal for EZDB U2, a 32 Kbyte RAM
RD1#
OUT
Read Strobe for EZDB U1
RD2#
OUT
Read Strobe for EZDB U2
PRD#
OUT
OR’d PSEN and RD
PF[3..0]
IO
General purpose 22V10 outputs (or inputs)
Other EZ-USB Signals
BKPT
OUT
EZ-USB Breakpoint output signal. Also buffered and connected to the green
“BKPT/Monitor” LED
WU#
OUT
EZ-USB Wakeup signal (from push-buttons)
