Z86D990 Datasheet, PDF (41/102 Pages) Zilog, Inc. – Low-Voltage Micro controllers with ADC

Z86D990/Z86D991 OTP and Z86L99X ROM
Low-Voltage Microcontrollers with ADC
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Figure 17. I-V Characteristics for the Current Sink Pad P43
The CPU reads the mode of the pad driver by reading bit number 2 from the LB
register. This bit is the output of a Set-Reset flip-flop that sets whenever the volt-
age on the pad is lower than V_outmin and is reset by a CPU write to the respective
register.
T1 Timer
The Z86D99/Z86L99 family provides one general-purpose 8-bit counter/timer, T₁,
driven by its own 6-bit prescaler, PRE₁. The T₁ counter/timer is independent of the
processor instruction sequence, which relieves software from time-critical opera-
tions such as interval timing and event counting.
The T₁ counter/timer operates in either single-pass or continuous mode. At the
end-of-count, counting either stops or the initial value is reloaded and counting
continues. Under software control, new values are loaded immediately or when
the end-of-count is reached. Software also controls the counting mode, how the
counter/timer is started or stopped, and the counter/timer’s use of I/O lines. Both
the counter and prescaler registers can be altered while the counter/timer is run-
ning.
PS003807-1002
PRELIMINARY