P89C668 Philips Semiconductors, P89C668 Datasheet - Page 45

• Manufacturer Part Number: P89C668
• Description: 80C51 8-bit Flash microcontroller family 64KB ISP FLASH with 8KB RAM
• Manufacturer: Philips Semiconductors

Philips Semiconductors
In-System Programming (ISP)
The In-System Programming (ISP) is performed without removing
the microcontroller from the system. The In-System Programming
(ISP) facility consists of a series of internal hardware resources
coupled with internal firmware to facilitate remote programming of
the P89C668 through the serial port. This firmware is provided by
Philips and embedded within each P89C668 device.
The Philips In-System Programming (ISP) facility has made in-circuit
programming in an embedded application possible with a minimum
of additional expense in components and circuit board area.
The ISP function uses five pins: TxD, RxD, V
Figure 46). Only a small connector needs to be available to interface
your application to an external circuit in order to use this feature.
The V
allowed to exceed datasheet limits.
Using the In-System Programming (ISP)
The ISP feature allows for a wide range of baud rates to be used in
your application, independent of the oscillator frequency. It is also
adaptable to a wide range of oscillator frequencies. This is
accomplished by measuring the bit-time of a single bit in a received
character. This information is then used to program the baud rate in
terms of timer counts based on the oscillator frequency. The ISP
feature requires that an initial character (an uppercase U) be sent to
the P89C668 to establish the baud rate. The ISP firmware provides
auto-echo of received characters.
Once baud rate initialization has been performed, the ISP firmware
will only accept Intel Hex-type records. Intel Hex records consist of
ASCII characters used to represent hexadecimal values and are
summarized below:
In the Intel Hex record, the “NN” represents the number of data
bytes in the record. The P89C668 will accept up to 16 (10H) data
bytes. The “AAAA” string represents the address of the first byte in
2001 Jul 27
80C51 8-bit Flash microcontroller family
64KB ISP Flash with 8KB RAM
:NNAAAARRDD..DDCC<crlf>
PP
supply should be adequately decoupled and V
Figure 46. In-System Programming with a Minimum of Pins
SS
, V
CC
V
CC
, and V
PP
not
PP
RST
XTAL2
XTAL1
V
SS
(see
89C668
45
indicated by transmitting a “.” character out the serial port (displaying
the record. If there are zero bytes in the record, this field is often set
to 0000. The “RR” string indicates the record type. A record type of
“00” is a data record. A record type of “01” indicates the end-of-file
mark. In this application, additional record types will be added to
indicate either commands or data for the ISP facility. The maximum
number of data bytes in a record is limited to 16 (decimal). ISP
commands are summarized in Table 9.
As a record is received by the P89C668, the information in the
record is stored internally and a checksum calculation is performed.
The operation indicated by the record type is not performed until the
entire record has been received. Should an error occur in the
checksum, the P89C668 will send an “X” out the serial port
indicating a checksum error. If the checksum calculation is found to
match the checksum in the record, then the command will be
executed. In most cases, successful reception of the record will be
the contents of the internal program memory is an exception).
In the case of a Data Record (record type 00), an additional check is
made. A “.” character will NOT be sent unless the record checksum
matched the calculated checksum and all of the bytes in the record
were successfully programmed. For a data record, an “X” indicates
that the checksum failed to match, and an “R” character indicates
that one of the bytes did not properly program. It is necessary to
send a type 02 record (specify oscillator frequency) to the P89C668
before programming data.
The ISP facility was designed to that specific crystal frequencies
were not required in order to generate baud rates or time the
programming pulses. The user thus needs to provide the P89C668
with information required to generate the proper timing. Record type
02 is provided for this purpose.
WinISP, a software utility to implement ISP programming with a PC,
is available on Philips Semiconductors’ web site. In addition, at the
web site is a listing of third party commercially available serial and
parallel programmers.
P2.7
V
TxD
RxD
V
CC
PP
SU01113
+12V OR + 5V
+5V
TxD
RxD
V
“1”
SS
P89C668
Preliminary data