Power Monitor Circuit
http://www.motorola.com/computer/literature 5-13
5
Status Indicators
The MBX board includes eight on-board LEDs (DS1–DS8) to indicate
power levels; board, battery, and programming status; and CPU and PCI
activity. (See MBX LED Status Indicators on page 6-29 for a complete
description.) Six additional signals (five for Ethernet activity and one for a
hard disk drive) are available for external display via utility connector #1.
(See Utility Connector J16 on page 6-21.)
Power Monitor Circuit
The MBX is equipped with a power monitor circuit that monitors both the
+3.3V and the +5V currents. At power up, the power monitor asserts
HRESET# low until voltages reach their proper levels, then holds
HRESET# low an additional 350ms. HRESET# is kept low as long as
either voltage is inadequate.
During normal operation, if either voltage drops below acceptable limits
(5% for +5V and 10% for +3.3V), the power monitor asserts HRESET#
low until the proper voltage returns.
The Reset signal on utility connector #1 (J16) is routed to this circuit.
Peripheral I/O Controller
The MBX series embedded controller uses a 37C672 multi-function I/O
controller chip from Standard Microsystems to implement the on-board
peripheral functions of the standard version, namely, an asynchronous
serial port (COM1) for the console/terminal interface, IEEE 1284
bidirectional parallel port, floppy disk drive support, keyboard and mouse
interface.
Asynchronous Serial Port
The I/O controller provides for two asynchronous ports (COM1 and
COM2). Interface header J18 and serial transceivers are supplied on board
for the COM1 port. COM2 signals, though not directly implemented on the
MBX, are routed to utility connector #2 for user implementation. No
transceivers are included for COM2.
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