Remote-processing RPC-220 Instrukcja Użytkownika Pobierz pdf (Strona 19)

WRITING, DEBUGGING, AND SAVING PROGRAMS SECTION 3

Page 3-8

WRITING FOR C

Mem ory Models

Most C compilers have different memory models. They

are usually referred to as SMALL, COM PAC T, and

LARGE. The D unfield com piler has 5 m odels while

Keil has 3. The differ ences betw een the memor y models

have to do with where and how much data is stored and

how they are accessed. When selecting a memory

model, do not select one where code and data are

overlapped into a single 64K address space.

Do not use the SMALL or CO MPA CT models in the

Dunfield compiler. The TINY, MEDIUM, and LARGE

models are OK.

Memory Use

Most pr ogram s written for 8051 C PUs require relatively

little RAM for control (data logging does require a lot

more). C compilers use both internal and external RAM

to store variables. Internal RAM is faster to access,

although there is much less of it. You have about 32K

of external RAM for var iable space during development.

Set up your compiler so external RAM star ts at address

0x0000. During development, you can use up to address

0x7FBF. Addresses 0x7FC 0 to 0x7FFF are used by the

monitor. A ddresse s 0x8000 to 0xF FF F is where cod e is

executed in RAM . A ll of RAM in segmen ts 1-7 is

available for data storag e, although this is not directly

supported by the compiler.

The RP C-220 can access up to 512K of RA M. This is

done by selecting a RAM segment the reading or writing

to it. See MEM220. C under M EM220 directory,

functions speek, spoke, spokew, speekw for exam ple

access.

Other Considerations for Writing and Saving

Programs

Starting address

All demonstration programs use a starting address of

0x8000. You can put programs into RAM anywhere

from 0x8000 to 0xff00 (the last 256 bytes are used by the

SAVE com mand).

Interrupts

The monitor ROM vectors all interrupts to RAM.

Simply add 0x8000 to the C PU' s interrupt base addr ess.

When an interrupt is serviced, the monitor ROM vectors

off to RAM. The jump code in RAM then jumps to the

appropriate location. When compiling for the final

version, the jump codes in RAM ar e replaced with

vector addresses only.

Reprogramming

See "WRITING C ODE FOR U PDATES" above for

more information.

USING DEMONSTRATION PROGRAMS

Demo programs and batch files were written for

Dunfield Development systems C compiler. A freeware

assembler, ASM51, is included and is in the root

directory. If you use another compiler you must modify

the code accordingly.

Demonstration programs are in separate director ies.

Each directory has source, output (hex), and batch files

for C. All are ready to run.

Batch and sour ce files assum e the Dun field comp iler is

used. Switches used in the command line may not work

with other compilers or assemblers. When you order a

compiler or development system from us, we will send

you library and include files to make the start up code.

In general, startup code was modified to instruct the

compiler where to begin assem bly and include interru pts

particular to the CPU type used.

PROGRAMS LARGER THAN 32K

The largest program that can be developed on the

RPC-220 is 32K. This is because the RAM allocated for

development is 32K and the flash EPROM is 32K.

It is possible to develop and put up to 64K of code in the

RPC-220. You must do three things to make this happen:

1 Use an EPROM em ulator. Rem ove the flash from

U3 and install the emulator. Set the emulator for a

64K EPROM (27C512). Make sure you m ake the

modifications described in 2 below.

2 Cut a trace (write line) on the circuit side to Jumper

W5. Refer to Figure 3-3 below.

1 2 ... 14 15 16 17 18 19 20 21 22 23 24 ... 46 47

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