NavCom LAND-PAK Rev.N User Manual

Page 95

Technical Reference Manual Rev. N

Blk = All;

Blu = IOP w/Internal Radio

;

Red = IOP & LBM

;

Grn = Engine only

0x01 – Directory (of files specified by name)

Obtaining a directory of files on the file system generally involves multiple requests. To
initiate a directory request, the user should send a directory request specifying a file name
mask and setting page number equal to zero. The IOP will respond with a message
containing up to 18 directory entries matching the specified file name mask. If there are
additional matching entries, bit 2 of W5 will be set to zero, indicating “this is not the final
page.” In this case, the user should send another request identical to the previous request
except with the page number incremented by 1. The IOP will then respond with the next 18
matching entries. This process continues until an IOP response is received with B2=1 in
W5. At that time, the user has received directory entries for all matching files.

In order to preserve word alignment, the length of each file name, including null terminators,
should be even. If necessary, an extra null terminator (‘\0’ character) should be appended
to support this requirement. For example, a file name TEST.TXT consists of eight
characters plus a null terminator, for a total of nine. An extra null terminator should be
added in this case to bring the total number of bytes to ten. The same convention will be
used for the file names in the response message.

Request

Record
Usage

Command - Yes
Response – No

Input: DOS file directory request;
Output: see table below

Ref

Message Field Description

Data Type Units

Range

Scale

Byte

Count

STX

(hex)

U08

PRA1 99 (hex)

U08

PRA2 66 (hex)

U08

7e(hex)

U08

Length 0xXXXX

U16

Sub ID 0x01

U08

0x00 (request)

U08

Page Number

U16

File name or mask (Null

Terminated String)
Supports DOS 8.3 filenames.
Supports wild card characters
‘*’ and ‘?’
‘?’ – Single character wild card
‘*’ – String wild card

U08[]

1[]

CKSM Checksum

U08

ETX

(hex)

U08