DS2250(T)
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SERIAL BOOTSTRAP LOADER
The Serial Program Load Mode is the easiest, fastest, most reliable, and most complete method of
initially loading application software into the DS2250(T) nonvolatile RAM. Communication can be
performed over a standard asynchronous serial communications port. A typical application would use a
simple RS232C serial interface to program the DS2250(T) as a final production procedure. The hardware
configuration which is required for the Serial Program Load Mode is illustrated in Figure 3. Port pins 2.7
and 2.6 must be either open or pulled high to avoid placing the device in a parallel load cycle. Although
an 11.0592 MHz crystal is shown in Figure 3, a variety of crystal frequencies and loader baud rates are
supported, shown in Table 2. The serial loader is designed to operate across a 3-wire interface from a
standard UART. The receive, transmit, and ground wires are all that are necessary to establish
communication with the DS2250(T).
The Serial Bootstrap Loader implements an easy-to-use command line interface which allows an
application program in an Intel hex representation to be loaded into and read back from the device. Intel
hex is the typical format which existing 8051 cross-assemblers output. The serial loader responds to
single character commands which are summarized below:
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 V
PP
1 0 X
Security Set 1 0 0 V
PP
1 1 X
Verify 1 X X 1 0 0 X
Prog Expanded 1 0 0 V
PP
0 1 0
Verify Expanded 1 0 1 1 0 1 0
Prog MCON or Key registers 1 0 0 V
PP
0 1 1
Verify MCON registers 1 0 1 1 0 1 1
