Z86L78 Datasheet, PDF (31/59 Pages) Zilog, Inc. – IR/Low-Voltage Microcontroller

Zilog
Z86L78
IR/Low-Voltage Microcontroller
Input Circuit
sets the time-out status bit (CTR0 D5) and generates an
The edge detector monitors the input signal on P31 or P20. interrupt if enabled (CTR0 D1) (Figure 19). This completes
1 ^{Based on CTR1 D5-D4, a pulse is generated at the Pos one cycle. T8 then loads from TC8H or TC8L according to}
Edge or Neg Edge line when an edge is detected. Glitches the T8_OUT level, and repeats the cycle.
in the input signal which have a width less than specified
(CTR1 D3, D2) are filtered out.
The user can modify the values in TC8H or TC8L at any
time. The new values take effect when they are loaded.
T8 Transmit Mode
Care must be taken not to write these registers at the time
When T8 is enabled, the output of T8 depends on CTR1, the values are to be loaded into the counter/timer, to en-
D1. If it is 0, T8_OUT is 1. If it is 1, T8_OUT is 0.
sure known operation. An initial count of 1 is not al-
lowed (a non-function will occur). An initial count of 0
When T8 is enabled, the output T8_OUT switches to the _{will cause TC8 to count from 0 to %FF to %FE (Note, % is}
initial value (CTR1 D1). If the initial value (CTR1 D1) is 0, _{used for hexadecimal values). Transition from 0 to %FF is}
TC8L is loaded, otherwise TC8H is loaded into the _{not a time-out condition.}
counter. In Single-Pass Mode (CTR0 D6), T8 counts down
to 0 and stops, T8_OUT toggles, the time-out status bit Note: Using the same instructions for stopping the
(CTR0 D5) is set, and a time-out interrupt can be generat- counter/timers and setting the status bits is not rec-
ed if it is enabled (CTR0 D1) (Figure 18). In Modulo-N ommended. Two successive commands, first stopping
Mode, upon reaching terminal count, T8_OUT is toggled, the counter/timers, then resetting the status bits is neces-
but no interrupt is generated. Then T8 loads a new count sary. This is required because it takes one counter/timer
(if the T8_OUT level now is 0), TC8L is loaded; if it is 1, clock interval for the initiated event to actually occur.
TC8H is loaded. T8 counts down to 0, toggles T8_OUT,
TC8H Counts
T8_OUT
“Counter Enable” Command,
T8_OUT Switches To Its
Initial Value (CTR1 D1)
T8_OUT Toggles,
Time-Out Interrupt
Figure 20. T8_OUT in SIngle-Pass Mode
T8_OUT Toggles
TC8L
TC8H
TC8L
TC8H
TC8L
“Counter Enable” Command,
T8_OUT Switches To Its
Initial Value (CTR1 D1)
Time-Out Interrupt
Time-Out Interrupt
Figure 21. T8_OUT in Modulo-N Mode
DS97LVO0701
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