CT2579 datasheet(16/41 Pages) AEROFLEX

16 / 41 page

APPLICATION NOTE #108

Released 9/98

DATA STORAGE AND RETRIEVAL IN RAM

The storage and retrieval of data on RAM is optimized for fast processor accesses. The

data (Transmit or Receive) is stored with the first data word (Word #0) in memory location

#0n and the last data word (Word #n) in location 00. The processor reads the Command

word and extracts the T/R bit, subaddress, and word count bits as a pointer to the proper

memory location. The word count field is used as a down counter variable so that a Do Loop

routine is executed and then branched out at counter = 00. This may be more efficient in

some compilers than an up counter and comparing current loop counter with word count

field on every loop. The following section contains sample software pseudo code for data

handling. See Memory Map for further details.

SAMPLE SOFTWARE CODE

The following section contains sample pseudo-code for programming and operation the

SmaRT unit. The code most resembles Microsoft Quick Basic code (IBM DOS compatible)

for simplicity.

RETRIEVING OR LOADING DATA TO RAM

REM *******************************************************************************************

REM *

Routines for operation in Remote Terminal (RT) Mode

REM *

REM ********************************************************************************************

REM *

Variables

REM *

_______

REM *

NCMDEMPTY

0 = EMPTY (NO Command WORDS IN FIFO)

REM *

1 = HAVE COMMAND WORDS IN FIFO

REM *

This signal is derived from NEMPTY

REM *

on the CT2577.

REM *

MODE

0 = RT MODE

REM *

1 = BC MODE

REM *

CMDWORD = COMMAND WORD READ FROM FIFO

REM *

WORDCNT = LOWER 5 BIT OF COMMAND WORD

REM *

INDICATES HOW MANY DATA WORDS

REM *

DATA() = DATA ARRAY (32 WORDS MAX)

REM *

MEMPOINT = LOWER 11 BITS OF THE COMMAND WORD

REM *

T/R_BIT = BIT #10 OF THE COMMAND WORD

REM *

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