33993 Datasheet, PDF (13/28 Pages) Freescale Semiconductor, Inc – Multiple Switch Detection Interface

FUNCTIONAL DEVICE OPERATION
LOGIC COMMANDS AND REGISTERS
LOGIC COMMANDS AND REGISTERS
PROGRAMMABLE SWITCH REGISTER
Inputs SP0 to SP7 may be programmable for switch-to-
battery or switch-to-ground. These inputs types are defined
using the settings command (refer to Table 5). To set an SPn
input for switch-to-battery, a logic [1] for the appropriate bit
must be set. To set an SPn input for switch-to-ground, a logic
[0] for the appropriate bit must be set. The MCU may change
Table 5. Settings Command
or update the Programmable Switch Register via software at
any time in Normal mode. Regardless of the setting, when the
SPn input switch is closed a logic [1] will be placed in the
Serial Output Response Register (refer to Table 16,
page 17).
Settings Command
Not used
Battery/Ground Select
23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0 0 0 0 0 0 0 1 X X X X X X X X sp7 sp6 sp5 sp4 sp3 sp2 sp1 sp0
WAKE-UP / INTERRUPT REGISTER
The Wake-Up / Interrupt Register defines the inputs that
are allowed to wake the 33993 from Sleep mode or set the
INT pin low in Normal mode. Programming the wake-up /
interrupt bit to logic [0] will disable the specific input from
generating an interrupt and will disable the specific input from
Table 6. Wake-Up / Interrupt Command
waking the IC in Sleep mode (refer to Table 6). Programming
the wake-up /interrupt bit to logic [1] will enable the specific
input to generate an interrupt with switch change of state and
will enable the specific input as wake-up. The MCU may
change or update the Wake-Up / Interrupt Register via
software at any time in Normal mode.
Wake-Up /Interrupt Command
Command Bits
23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0 0 0 0 0 0 1 0 X X X X X X X X sp7 sp6 sp5 sp4 sp3 sp2 sp1 sp0
0 0 0 0 0 0 1 1 X X sg1 sg1 sg1 sg1 sg9 sg8 sg7 sg6 sg5 sg4 sg3 sg2 sg1 sg0
3210
WETTING CURRENT REGISTER
The 33993 has two levels of switch contact current, 16 mA
and 2.0 mA (see Figure 10). The metallic command is used
to set the switch contact current level (refer to Table 7).
Programming the metallic bit to logic [0] will set the switch
wetting current to 2.0 mA. Programming the metallic bit to
logic [1] will set the switch contact wetting current to 16 mA.
The MCU may change or update the Wetting Current
Register via software at any time in Normal mode.
Wetting current is designed to provide higher levels of
current during switch closure. The higher level of current is
designed to keep switch contacts from building up oxides that
form on the switch contact surface.
Switch Contact Voltage
16 mA Switch Wetting Current
2.0 mA Switch Sustain Current
20 ms Wetting Current Timer
Figure 10. Contact Wetting and Sustain Current
Analog Integrated Circuit Device Data
Freescale Semiconductor
33993
13