CPU OPERATION
POWER CONSUMPTION
The 4C27 is an all-CMOS CPU, so overall power consumption is typically less than 2 watts (about
350 mA). If the lowest power consumption is necessary, the CPU clock can be stopped when not
active. This can reduce the CPU power to less than 100 mA. It is the responsibility of the application
program to stop the CPU when idle. An example program (STOPCLK.COM) is provided to
demonstrate stopping the CPU clock. If the absolute lowest power consumption is required, Mesa
can supply a version of the 4C27 that uses a lower power PAL. Please contact MESA for more
information on this low power CPU version.
STARTUP ERRORS
The BIOS performs a variety of system tests at startup. Serious problems are reported by beep
codes. The red LED is also flashed at the same time as the speaker beep. The BIOS beep codes are as
follows:
BEEPS
ERROR
2
Bad external ROM checksum
3
External ROM initialization error
4
No system memory found
5
Can't boot - no resident language
6
BIOS ROM checksum error
7
Bad local RAM
8
VGA ROM initialization faulure
9
Invalid system configuration data (or forced default)
10
No ROM BIOS image found
11
Corrupted BIOS module found
WATCHDOG TIMER
The 4C27 is intended mainly for embedded system applications where there is no one to hit the
reset switch should something go awry. To prevent a crashed or otherwise hung system from
remaining so indefinitely, the 4C27 is provided with a built in watchdog timer that will reset the 4C27
if not 'fed' regularly. The time-out period of this counter is a minimum of 500 milli-seconds. The
default INT 1C (user tic clock) task 'feeds' the watchdog. User software must be careful not to disable
interrupts for more than these time periods or the watchdog may bite!
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4C27 CPU USER'S MANUAL