__Detailed Description of Software

EPROM Resident Program

A small bootstrap program is stored in the EPROM locat-

ed on the 68HC16 board. The EPROM resident program

initializes the 68HC16, tests the static RAM, configures

the chip-select logic, establishes serial communications

with the host, and downloads program KIT194 into RAM.

It starts operating on power-up or whenever the RESET

button is pressed. After RESET, it tests the RAM, then

waits to receive a serial character on its serial port before

transmitting its identification banner.

RAM Resident Program

KIT194.S19 is a 68HC16 RAM-resident program that is

transferred from disk to the static RAM on the 68HC16

module. When the KIT194 program is running, it offers

the commands listed in Table 2.

Personal Computer Program

MAX194.EXE, which runs on an IBM-compatible com-

puter, is a terminal program that establishes communi-

cation with the 68HC16 module and allows the user to

download and run the Maxim-provided RAM resident

program. The serial communication baud rate is initiat-

ed at 1200 baud (default setting) to ensure proper

operation with basic systems.

The MAX194.EXE program provides several commands

that are associated with the host computer. These com-

mands are listed in Table 4.

The MAX194.EXE program can store the text of a termi-

nal session in a log file. To begin recording the terminal

session, press ALT+O [the letter O]. The program will

ask for a file name. Press ENTER to accept the default

file name, or type in a different name. If a file with that

name already exists, the old file will be erased. To close

the file, press ALT+C. The log file will contain the com-

plete text of the terminal session from the time the file is

opened until it is closed.

Using the QSPI to Read the MAX194

The 68HC16 module uses its Queued Serial Peripheral

Interface (QSPI) in master mode to read the MAX194.

The MAX194 EV kit software uses the algorithm

described below. Refer to the example program of

Listing 1, which assigns QSPI entries 0 and 1 and pro-

grammable chip-select PCS0 to the MAX194. Note:

This interface scheme requires that the QSPI clock be

active during the MAX194 reset (see Reset and

Calibration Procedure section).

1) Initialize the QSPI parameters as follows:

2) Verify that EOC is low before starting the conversion.

3) Start the QSPI transfer.

4) Wait until QSPI transfer is complete. The CPU may

perform other tasks while waiting.

5) Extract the significant bits from QSPI RAM. Bits

B13–B06 are located in QSPI receive RAM entry

RR0 bits 7–0, and bits B05–B00 are located in entry

RR1 bits 9–4. RR1 bits 3–2 are the sub-LSB bits of

the MAX194 (see Table 5).

MAX194 Evaluation System/Evaluation Kit

4

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Table 4. Commands Available in

MAX194.EXE Terminal Program

KEY

COMMAND

ALT+L

Load and run resident code on 68HC16.

ALT+X

Exit to DOS.

ALT+P

Change port (COM1, COM2).

ALT+R

Send RESET command to 68HC16.

ALT+O

Open a log file.

ALT+C

Close the log file.

ALT+B

Display baud rate menu.

ALT+1

1200 baud

ALT+4

4800 baud

ALT+9

9600 baud

19200 baud

ALT+2

PARAMETER

VALUE

EXPLANATION

SPBR

5

1.68MHz serial clock

CPOL

0

Serial clock is low when idle

CPHA

1

CPOL

≠ CPHA, data valid on

falling clock edge

BITS

$0A

Ten bits per QSPI transfer. Use

two consecutive QSPI transfers

to read the MAX194.

DSCKL

2

Delay 119ns between CS and first

clock in the first QSPI transfer to

COMD.0

$D0

Control RAM for first QSPI trans-

fer: CONT = 1, BITSE = 1, DTL =

0, DSCK = 1, PSC0 = 0

COMD.1

$40

Control RAM for second QSPI

transfer: CONT = 0, BITSE = 1,

DTL = 0, DSCK = 0, PSC0 = 0

NEWQP

0

Index of first queue entry to

execute

ENDQP

1

Index of last valid queue entry