HT82K68 Holtek Semiconductor Inc, HT82K68 Datasheet - Page 18

• Manufacturer Part Number: HT82K68
• Description: Multimedia Keyboard Encoder OTP
• Manufacturer: Holtek Semiconductor Inc

Each I/O line has its own control register (PAC,
PBC, PCC, PDC, PEC) to control the input/out-
put configuration. With this control register,
CMOS output or schmitt trigger input with or
without pull-high resistor (mask option) struc-
tures can be reconfigured dynamically (i.e.,
on-the-fly) under software control. To function as
an input, the corresponding latch of the control
register must write ²1². The pull-high resistance
will exhibit automatically if the pull-high option
is selected. The input source(s) also depend(s) on
the control register. If the control register bit is
²1², input will read the pad state. If the control
register bit is ²0², the contents of the latches will
move to the internal bus. The latter is possible in
²read-modify-write² instruction. For output func-
tion, CMOS is the only configuration. These con-
trol registers are mapped to locations 13H, 15H,
17H, 19H and 1BH.
Preliminary
Input/output ports
18
After a chip reset, these input/output lines stay
at high levels or floating (mask option). Each
bit of these input/output latches can be set or
cleared by the SET [m].i or CLR [m].i (m=12H,
14H, 16H, 18H or 1AH) instruction.
Some instructions first input data and then fol-
low the output operations. For example, the
SET [m].i, CLR [m].i, CPL [m] and CPLA [m]
instructions read the entire port states into the
CPU , e xec ute the define d o pe ra tio ns
(bit-operation), and then write the results back
to the latches or the accumulator.
Each line of port A and port C [0:3] has the capa-
bility to wake-up the device.
HT82K68E
August 8, 2000