6 ' 1999 Scenix Semiconductor, Inc. All rights reserved. www.scenix.com Table 5 FUSEX Bits for SX18/20/28AC with Datecode Axyywwxx (new revision) 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. OPTIONX/
STACKX OPTION Register Extension and Stack Extension. Set to 1 to disable the pro-
grammability of bit 6 and bit 7 in the OPTION register, the RTW and RTE_IE
bits (in other words, to force these two bits to 1); and to limit the program stack
size to two locations. Clear to 0 to enable programming of the RTW and RTE_IE
bits in the OPTION register, and to extend the stack size to eight locations. 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. The BOR1:BOR0 bits enable or disable the brown-out reset
function and set the brown-out threshold voltage as follows:
00 = 4.2V
01 = 2.6V
10 = 2.2V
11 = Disable Brown-Out Reset BORTRIM1:
BORTRIM0 Brown-Out trim bits (parts are shipped out of the factory untrimmed). BP1:
BP0 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 BP1:BP0 settings:
00 = 1 page, 1 bank
01 = 1 page, 2 banks
10 = 4 pages, 4 banks
11 = 4 pages, 8 banks (default)