' 1999 Scenix Semiconductor, Inc. All rights reserved. 5 www.scenix.com Table 4 FUSEX Bits for SX18/20/28AC with Datecode yywwxx (old revisions) Option Bits Description IRCTRIM2:
IRCTRIM0 Internal RC Oscillator Trim. This 3-bit field adjusts the operation of the internal
RC oscillator to make it operate within the target frequency range of 4.0 MHz
plus or minus 8%. Parts are shipped from the factory untrimmed. The device
relies on the programming tool to provide the trimming function. CF Carry Flag Input. Set to 1 to ignore the carry flag as an input to addition and sub-
traction operations. Clear to 0 to add the carry flag into all addition operations
(ADD fr,W means fr = fr + W + C); and to subtract the complement of the carry
flag from all subtraction operations (SUB fr,W means fr = fr   W   /C). BOR1:
BOR0 Brown-Out Reset. These two factory-configured bits should not be changed
unless you want to enable the brown-out functionality of the device. To enable
the brown-out feature (4.2V trip level), set these bits to 01. To disable the brown-
out feature set both bits to 1. RAM1:
RAM0 Configured Number of RAM Banks. These two factory-configured bits should
not be changed unless you want to reduce the configured amount of RAM in the
device. To do so, use one the following RAM1:RAM0 settings:
00 = 1 bank
01 = 2 banks
10 = 4 banks
11 = 8 banks (default) MEM1:
MEM0 Configured Memory Size. These two factory-configured bits should not be
changed unless you want to reduce the configured amount of program memory in
the device. To do so, use one the following MEM1:MEM0 settings:
00 = 1 page
01 = 1 page
10 = 4 pages
11 = 8 pages (default)