Specifications

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[ 3 ] Calculating Memory Requirements
The FTP protocol specifications do not provide for checking the amount of BHT memory avail-
able during downloads. If the BHT runs out of memory during a download, the FTP client can-
cels the transfer and deletes the partially downloaded file. The user application program must,
therefore, check availability with the
FRE function or equivalent method and compare the result
with the BHT file size (BFS) before using the download function. The formula for calculating the
BHT memory requirements (MEM) depends on the file format.
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User Programs (*.PD3)
Determine MEM from HFS.
BFS = ROUND_UP (HFS ÷ (128 + LDS)) × 64
MEM = ROUND_UP (BFS ÷ 4096) × 4096
Example: File size of 12,345 bytes on operating system using CR-LF combination
BFS = ROUND_UP (12345 ÷ (128 + 2)) × 64 = ROUND_UP(94.96) × 64 = 6080
MEM = ROUND_UP (6080 ÷ 4096) × 4096 = ROUND_UP(1.48) × 4096 = 8192
Note that 128K of free memory is enough to download even the largest (128K) BASIC pro-
gram.
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Extension Libraries (*.FN3 and *.EX3)
Determine MEM from HFS.
BFS = ROUND_UP (HFS ÷ (130 + LDS)) × 64
MEM = ROUND_UP (BFS ÷ 4096) × 4096
The rest of the procedure is the same as for BASIC program files.
NOTE
• The line delimiter size (LDS) refers to the number of bytes in each line delimiter:
two for operating systems using the CR-LF combination and one for those using
only LF or CR.
• The number 4096 (4K) is the assumed memory management unit. Change this to
8192 (8K) if the BHT uses that larger block size.
• HFS = host file size