Remote-processing RPC-2350 Manuel d'utilisateur télécharger pdf (Page 32)

DATA MEMORY CHAPTER 5

5-6

default values (from the program) should be used, since

it is uncertain if the first or second set is corrupted.

Both data sets would then be re-initialized.

A triplicate set is used to recover the last set or indicate

that the data in the first set is valid. The pr ocedure and

logic is as follows.

Data is written to each element in a set in a specific and

consistent order (data to an entire set does not have to be

written to, just that element). For example, a calibration

constant is saved (POKE' d) in three different places.

Assume that the constant was assigned address 0, 100,

and 200 in segment 1. The data is POKEd to address 0

first, then 100, then 200.

Upon reset, the calibration value is checked. If the value

at address 0 agrees with address 100 and 200, then no

corruption occurred. When address 0 and 100 agree but

not 200, then this indicates that a reset occurre d while

updating the third set. The first data set can be trusted.

The third data set simply needs to be updated.

When the first two sets do not agree, then you know that

the first data is corrupted. If the second and third set

agree, then, depending upon the system r equireme nts,

the first set could be "corrected" using the old data. The

user or other device could be alerted that a calibration

(or other ) must be performed again. W hen all thre e sets

disagree, then you must take action appropriate to the

situation.

Another technique to ch eck for valid mem ory is

checksum s. Sim ply write a progr am to add the values in

RAM and compare it against a number is a good check.

However, you cannot tell which data element was

corrupted.

Instances of data corruption are rar e. T hey do increase

as the board power is cycled or reset.

ASSEMBLY LANGUAGE INTERFACE

Assembly language programs (including compiled C)

must start from segment 0. Use the CAMBASIC CALL

statement to execute an assembly language program.

A specific area of RAM should be reserved for the

program. This is to prevent strings and variables from

corrupting that area of RAM . Use the SYS(1) and

SYS(2) statements to do this. SYS(1) retur ns the lowest

memory location while SYS(2) returns the upper

location. Run the program first to make sure variable

memory has been allocated before running these SYS

commands. F ailure to do so may r esult in address

returned that are not really free for assembly language

program s.

There are sever al ways to put a program in mem ory,

depending upon your application.

1. Use DATA statements and POKE the code into

segment 0 RAM.

2. Write a program to download code. Some

applications are connected to a larger system which

"initializes" its systems. Using INKEY$ or COM $,

code is received and then poked into memory using

POKE$.

3. Read the code from the EPROM (U3) (using INP)

and transfer it to RAM (using POKE).

4. Some space is available in the CAMBASIC ROM.

Space from about 6B00H to 6F FF H is available in

version 1.4 of the 2350G board. The starting

address will proba bly change in the future w ith

different CAMBASIC versions. You may burn

your assembly language program in U1 and CALL

in from BASIC.

5. Space is available in the Flash EPROM. In theory

you can run directly from Flash. This involves

running in sectored areas unique to the Z180.

However, this is probably more effort. Use the

Flash to stor e the program and then transfer it to

RAM segment 0.

In all cases, it is best to load code into RAM from a

"secure" source, such as F lash EPROM . Even though

RAM is battery backed, over tim e there is the possibility

it could be corrupted.

Below is an example of loading and running an asse mbly

language program.

100 FOR N = &FB00 TO &FB0C

110 READ A

120 POKE N,A

130 NEXT

900 DATA &DB, 2, &47, &E6, &FE, &D3

910 DATA 2, &78, &F6, 1, &D3, 2, &C9

2000 CALL &FB00

Lines 100 to 130 load the program into RAM. DATA

statements may be entered manually.

1 2 ... 27 28 29 30 31 32 33 34 35 36 37 ... 82 83

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Remote-processing RPC-2350 Manuel d'utilisateur Page 32

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