DS2250(T)

8 of 20

COMMAND

FUNCTION

C

Return CRC-16 checksum of embedded RAM

D

Dump Intel hex File

F

Fill embedded RAM block with constant

K

Load 40-bit encryption key

L

Load Intel hex file

R

Read MCON register

T

Trace (Echo) incoming Intel hex data

U

Clear Security Lock

V

Verify Embedded RAM with incoming Intel hex

W

Write MCON register

Z

Set security lock

P

Put a value to a port

G

Get a value from a port

Table 1 summarizes the selection of the available Parallel Program Load cycles. The timing associated

with these cycles is illustrated in the electrical specs.

PARALLEL PROGRAM LOAD CYCLES Table 1

MODE

RST

PSEN

PROG

EA

P2.7

P2.6

P2.5

Program

1

0

0

10

X

Security Set

1

0

0

11

X

Verify

1X

X

1

00

X

Prog Expanded

1

0

0

01

0

Verify Expanded

1

0

1

1

0

1

0

Prog MCON or Key registers

1

0

0

01

1

Verify MCON registers

1

0

1

1

0

1

1

The Parallel Program cycle is used to load a byte of data into a register or memory location within the

DS2250(T). The Verify cycle is used to read this byte back for comparison with the originally loaded

value to verify proper loading. The Security Set cycle may be used to enable and the software security

feature. One may also enter bytes for the MCON register or for the five encryption registers using the

Program MCON cycle. When using this cycle, the absolute register address must be presented at Ports 1

and 2 as in the normal program cycle (Port 2 should be 00H). The MCON contents can likewise be

verified using the Verify MCON cycle.

When the DS2250(T) first detects a Parallel Program Strobe pulse or a Security Set Strobe pulse while in

the Program Load Mode following a power-on reset, the internal hardware of the device is initialized so

that an existing 4-kbyte program can be programmed into a DS2250(T) with little or no modification.

This initialization automatically sets the range address for 8 kbytes and maps the lowest 4-kbyte bank of

embedded RAM as program memory. The next 4 kbytes of embedded RAM are mapped as data memory.

In order to program more than 4 kbytes of program code, the Program/Verify Expanded cycles can be

used. Up to 32 kbytes of program code can be entered and verified. Note that the expanded 32 kbyte

Program/Verify cycles take much longer than the normal 4 kbyte Program/Verify cycles.