MAX186 Evaluation System/Evaluation Kit

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13

The MAX233 also generates the output voltages neces-

sary to drive RS-232 lines.

Port 0 (pins 32-39) of the 80C32 multiplexes the lower

eight bits of memory address and the eight bits of

read/write data. The lower eight bits of address data

are latched during each I/O cycle by the 74HCT573

octal latch. The latch is controlled by the address latch

enable (ALE) signal of the 80C32. Port 2 (pins 21-28) of

the 80C32 supplies the upper eight bits of address

information.

The port 3 pins (10-17) provide several unrelated func-

tions. Pins 10 and 11 are used as the receive data

(RxD) and transmit data (TxD) pins of the RS-232 link.

trol signals for the data I/O cycles. Four other pins are

configured as interrupt and timer controls, but are not

used on this board.

Memory

The board has a 27C64 EPROM containing code for ini-

tializing the 80C32 and downloading additional pro-

gram code to the 62256 RAM. After a reset, the EPROM

resident code initializes the 80C32, determines the

address range of the RAM, sets the RS-232 baud rate

to 1200, and waits for communications from the PC.

Receiving any character will prompt the program to

send an initial banner that includes the program name,

revision level, and boundaries of the on-board RAM.

The 62256 CMOS (32kbyte) static RAM is used to hold

program code for the various Maxim EV kits that use

the 80C32 module as the controller. Programs are

transferred from disk to the RAM using software run-

ning on a personal computer, such as MAXLOAD or

other programs provided with Maxim EV kits. Programs

written to execute from this RAM start at 4000 (HEX)

and are typically less than 4kbytes long. The remaining

RAM is available for data storage.

Address Ranges

Logic on the module board generates various enable

signals for different address ranges. The ROM and

RAM enable signals are fed directly to the respective

chips. Several additional signals (CS0-CS3) are avail-

able on the data connector to be used by Maxim EV

kits. Table 1 outlines the address range for each of the

elements found on the 80C32 module.

Table 1. Address Ranges in Hexadecimal

ADDRESS RANGE (HEX)

ENABLE SIGNAL

0000

 

3FFF

ROM

4000

 

BFFF

RAM

C000

 

CFFF

CS0

D000

 

DFFF

CS1

E000

 

EFFF

CS2

F000

 

FFFF

CS3

Data I/O Connector

A 40-pin connector mounted on the edge of the printed

circuit board provides connection between the µC

module and other Maxim EV kits. Both power and digi-

tal signals are transferred via the connector. To join the

module board with an EV kit, carefully align and insert

the pins on the connector with the mating 40-pin female

connector of the kit. The pin functions are listed in

Table 2.

Table 2. I/O Connector Pin Functions

PIN

FUNCTION

DESCRIPTION

1-4

Ground

5, 6

Pre-regulator input

7, 8

Regulated +5V

9

RD

Read strobe

10

WR

Write strobe

11

CS0

Address C000-CFFF

12

CS1

Address D000-DFFF

13

CS2

Address E000-EFFF

14

CS3

Address F000-FFFF

15-18

ADDR0-ADDR3

Lowest 4 bits of address

19-26

DB0-DB7

8-bit data bus

27-34

P1.0-P1.7

8 bits of port 1

35-40

Reserved