Serial Ports (One Dual Mode Rs-232 / Irda); Clock/Calendar; Ps2 Keyboard Port; The Three Stooges - GE MAC 5000 Service Manual

RS-232 Serial Ports (One Dual Mode RS-232 / IrDA)

Clock/Calendar

PS2 Keyboard Port

The Three Stooges

2-30
Equipment Overview: Theory of Operation
Four serial ports are provided on two back panel Mini-DIN 8 pin
connectors. The Super I/O device provides two serial ports (COM1 and
COM2) and two more (COM3 and COM4) are provided by the ATMEL
CPU. The COM2 serial port and modem handshake lines are found in
the COM2 connector. COM1, COM3, and COM4 serial ports use pins in
the COM1 connector. The COM2 serial port of the Super I/O device also
supports the IrDA interface. The COM1 serial port from Super I/O is
multiplexed with serial debug port of ATMEL. The multiplexer select
pins are controller by the jumper(W2) setting. Other than the above
mentioned COM ports, an additional com port, COM5 is provided by
ATMEL. This is terminated to daughter board interface connector and is
used by the communication board Ethernet module.
RS-232 level shifting is provided by two transceivers. Each produces the
necessary drive voltages with internal charge pumps. The devices are
rated to withstand ESD onslaught, so no external ESD protection is
provided. The transceivers may be shut down under software control to
conserve power.
The Super I/O device provides a clock /calendar function. Backup battery
power is provided by a "super" capacitor (C21) with sufficient storage
capacity to power the clock for hours after main battery removal. This
backup source provides sufficient time to exchange battery packs when
necessary. Diode CR106 charges C21 when the main system power is up.
R181 limits the charging current to a safe level.
External card / bar code readers may be connected to the MAC 5000 via
a PS-2 compatible keyboard port. A small amount of 5V power is
available at the connector to power the external device. Power faults
are detectable. EMI and ESD protection are provided.
System management and some low level I/O functions are implemented
in preprogrammed 68HC05 microcontrollers. Moving some I/O functions
out into small processors relieves the ATMEL CPU of burdensome real-
time chores and moves the control hardware closer to the controlled
devices, potentially reducing EMI. Localizing control also promotes reuse
in future designs as the functions are self contained and reasonably
portable.
Originally there were four Stooges. Since the boot loading and FPGA
configuration is handled by ATMEL CPU, the Curly was removed in -006
board. Although there are three of these little fellows in the MAC 5000,
each performing a different function, there is only one firmware image.
By merging the code from each of the three functions into a single ROM
image, cost and confusion are reduced. It is impossible to place a
MAC™ 5000 resting ECG analysis system
2024917-010
Revision B