Boot ROM

The boot ROM, U3, is configured as an 8-bit memory

device. Resistor R4 pulls data bit 0 low during system

reset, forcing the µC to fetch instructions using only the

upper eight data bits. The boot ROM checks the sys-

tem and waits for commands from the host. Refer to the

EV kit manual for specific start-up procedures.

Software

All software is supplied on a disk with the EV kit.

Instructions for operating the software are included in

the EV kit manual. Refer to the EV kit manual for more

information.

_______68HC16 Module Self Check

To test the 68HC16 module’s integrity, connect the

power supply to the power terminals (J2). Do not con-

nect anything to J1 or J3. Slide the power switch SW1

to the “ON” position. The LED will light up, and will flash

within 5 seconds.

If the LED flashes with a 50%-on/50%-off duty cycle,

then it passed its self check. Note that this test does

not exercise the RS-232 port or the EV kit 40-pin inter-

face, but it does confirm that the power supply, micro-

processor, ROM, and RAM passed the self test.

If the LED flashes with a 10%-on/90%-off duty cycle,

then it failed its self check. Most likely, the RAM chip

(U5) is bad.

If the LED remains on and does not flash, then the

problem is either U3 (the EPROM), U1 (the micro-

processor), U4 (the regulator), the MAX707 reset gen-

erator, or the power supply. Use a voltmeter to verify

that the power supplies are good. Check the power-

supply input and the +5V output from the regulator.

Use an oscilloscope to see if the 32.768kHz reference

oscillator is running.

MAX194 Evaluation System/Evaluation Kit

______________________________________________________________________________________

17

Table 11. 68HC16 Module Memory Map

(all address values are in 20-bit hex)

Shadow of boot ROM

08000–0FFFF

Shadow of user RAM

18000–1FFFF

User RAM (U5, strobed by CS0 and CS2)

10000–17FFF

Unused

20400–7DFFF

Internal standby RAM; 1kbyte

20000–203FF

Not accessed by the 68HC16

80000–F7FFF

External chip select (J1 pin 11) (CS7)

7E000–7E7FF

External chip select (J1 pin 12) (CS8)

7E800–7EFFF

External chip select (J1 pin 13) (CS9)

7F000–7F7FF

External chip select (J1 pin 14) (CS10)

7F800–7FFFF

Unused

F8000–FF6FF

68HC16’s built-in ADC (not used)

FF700–FF73F

Unused

FF740–FF8FF

General-purpose timer module (GPT)

Boot ROM (U3, strobed by CSBOOT)

FF900–FF93F

00000–07FFF

FUNCTION

Unused

PIN

FF940–FF9FF

System integration module (SIM)

FFA00–FFA7F

Unused

FFA80–FFAFF

Internal standby RAM (SRAM)

control registers

FFB00–FFB07

Unused

FFB08–FFBFF

Queued serial module (QSM)

FFC00–FFDFF

Unused

FFE00–FFFFF