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PDF AN440 Data sheet ( Hoja de datos )
| Número de pieza | AN440 | |
| Descripción | RAM Loader Program | |
| Fabricantes | Philips | |
| Logotipo |  |
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Philips Semiconductors Microcontroller Products
RAM loader program for 80C51 family applications
Application note
AN440
Author: Greg Goodhue
The following program allows an 80C51
family microcontroller to load most of its code
into a RAM over a serial link after power up
and execute out of the RAM for normal
operation. This can allow a final product to
have firmware updates done by a simple
diskette mailing. Such a program is often
called a “bootstrap loader”.
For this example, it is assumed that the code
download is done via a serial communication
link, although the program could be adapted
to other forms of download. The comments at
the beginning of the listing are intended to
document the program and its use
completely.
An additional comment would be that any
static routines (low level routines that are
unlikely to change over time) can probably be
put into the permanent program memory
(on-chip or off-chip ROM or EPROM) along
with the bootstrap loader to save program
RAM space for other things.
The source code file for this program is
available for downloading from the Philips
computer bulletin board system. This system
is open to all callers, operates 24 hours a
day, and can be accessed with modems at
2400, 1200, and 300 baud. The telephone
numbers for the BBS are: (800) 451-6644 (in
the U.S. only) or (408) 991-2406.
Basic Diagram of RAM Connections for the Boot Loader
80/87C51
containing the boot
loader program (or use
external EPROM)
P2
ALE
serial
communication
to host
RxD
TxD
P0
WR
RD
PSEN
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addr
latch
Program
RAM
high
address
low
address
data
WR
RD
CE
(decode from
high order
address lines)
DataShee
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June 1993
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Philips Semiconductors Microcontroller Products
RAM loader program for 80C51 family applications
; All conditions are met, so hope the data file and the GO address are all
; correct, because now we’re committed.
MOV
ACALL
JNB
PUSH
PUSH
RET
A,#’@’
PutChar
TI,$
LowAddr
HighAddr
; Send confirmation to GO. ” @ ”
; Wait for completion before GOing.
; Put the GO address on the stack,
; so we can Return to it.
; Finally, go execute the user program!
;=============================================================================
; Hexadecimal File Input Routine
;=============================================================================
HexIn:
CLR
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
MOV
SETB
A
State,A
Flags,A
HighAddr,A
LowAddr,A
HASave,A
LASave,A
ChkSum,A
FilChkHi,A
FilChkLo,A
EFlags,A
ErrFlag4
; Clear out some variables.
; Start with a ’no data’ condition.
et4U.com
StateLoop:
ACALL
ACALL
MOV
ACALL
JNB
GetChar
; Get a character for processing.
AscHex
; Convert ASCII–hex character to hex.
Ch,A
; Save result for later.
GoState
; Go fDiandtaSthheeente4xUt.csotmate based on
; this char.
DoneFlag,StateLoop ; Repeat until done or terminated.
ACALL
MOV
ACALL
MOV
ACALL
MOV
ACALL
MOV
ACALL
ACALL
RET
PutChar
A,#’(’
PutChar
A,FilChkHi
PrByte
A,FilChkLo
PrByte
A,#’)’
PutChar
CRLF
; Send the file checksum back as
; confirmation. ” (abcd) ”
; Exit to main program.
; Find and execute the state routine pointed to by ”State”.
GoState:
MOV
ANL
RL
MOV
JMP
A,State
A,#0Fh
A
DPTR,#StateTable
@A+DPTR
; Get current state.
; Insure branch is within table range.
; Adjust offset for 2 byte insts.
; Go to appropriate state.
StateTable: AJMP
AJMP
AJMP
AJMP
AJMP
AJMP
AJMP
AJMP
AJMP
AJMP
AJMP
AJMP
AJMP
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AJMP
AJMP
AJMP
StWait
StLeft
StGetCnt
StLeft
StGetAd1
StLeft
StGetAd2
StLeft
StGetRec
StLeft
StGetDat
StLeft
StGetChk
StSkip
BadState
BadState
; 0 – Wait for start.
; 1 – First nibble of count.
; 2 – Get count.
; 3 – First nibble of address byte 1.
; 4 – Get address byte 1.
; 5 – First nibble of address byte 2.
; 6 – Get address byte 2.
; 7 – First nibble of record type.
; 8 – Get record type.
; 9 – First nibble of data byte.
; 10 – Get data byte.
; 11 – First nibble of checksum.
; 12 – Get checksum.
; 13 – Skip data after error condition.
; 14 – Should never get here.
; 15 – ”
”””
June 1993
DataSheet4 U .com
5
Application note
AN440
DataShee
5 Page | ||
| Páginas | Total 9 Páginas | |
| PDF Descargar | [ Datasheet AN440.PDF ] | |
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