45111 Datasheet, PDF (174/184 Pages) List of Unclassifed Manufacturers – 14-DAY MONEY BACK GUARANTEE

15 Appendix E: SX Data Sheet
15.4.3 Option
The OPTION register is a run-time writable register used to configure the RTCC and the Watchdog
Timer. The size of this register is affected by the OPTIONX device setting.
OPTION
76543210
RTW RTI RTS RTE PSA PS2 PS1 PS0
When OPTION Extend = 0, bits 7 and 6 are implemented.
When OPTION Extend = 1, bits 7 and 6 read as ‘1’s.
RTW - If = 0, register $01 is W
If = 1, register $01 is RTCC
RTI - If = 0, RTCC roll-over interrupt is enabled
If = 1, RTCC roll-over interrupt is disabled
RTS - If = 0, RTCC increments on internal instruction cycle
If = 1, RTCC increments on transition of RTCC pin
RTE - If = 0, RTCC increments on low-to-high transition
If = 1, RTCC increments on high-to-low transition
PSA - If = 0, prescaler is assigned to RTCC, divide rate determined by PS0-PS2 bits
If = 1, prescaler is assigned to WDT, and divide rate on RTCC is 1:1
Figure 36 - Prescaler Division Ratios
PS2, PS1, PS0
000
001
010
011
100
101
110
111
RTCC
Divide Rate
1:2
1:4
1:8
1:16
1:32
1:64
1:128
1:256
Watchdog Timer
Divide Rate
1:1
1:2
1:4
1:8
1:16
1:32
1:64
1:128
15.4.4 Fuse Registers
The Fuse registers are accessible only at program time. The SX-Key Development System Software
provides a convenient interface that is easy to use to customize the SX. You may use the predefined
Page 174 • SX-Key/Blitz Development System Manual 2.0 • Parallax, Inc.