Z86E7216PSC View Datasheet(PDF) - Zilog
Part Name
Description
MFG CO.
'Z86E7216PSC' PDF : 74 Pages View PDF
Z8 Data Bus
Pos Edge
Neg Edge
HI8
CTR0 D4, D3
SCLK
Clock
Select
Clock
8-Bit
Counter T8
CTR0 D2
LO8
Z86E72/E73
OTP IR Microcontrollers
1
IRQ4
CTR0 D1
T8_OUT
Z8 Data Bus
TC8H
TC8L
Figure 26. 8-Bit Counter/Timer Circuits
Input Circuit
The edge detector monitors the input signal on P31 or P20.
Based on CTR1 D5-D4, a pulse is generated at the Pos
Edge or Neg Edge line when an edge is detected. Glitches
in the input signal which have a width less than specified
(CTR1 D3, D2) are filtered out.
T8 Transmit Mode
When T8 is enabled, the output of T8 depends on CTR1,
D1. If it is 0, T8_OUT is 1. If it is 1, T8_OUT is 0.
When T8 is enabled, the output T8_OUT switches to the
initial value (CTR1 D1). If the initial value (CTR1 D1) is 0,
TC8L is loaded, otherwise TC8H is loaded into the
counter. In Single-Pass Mode (CTR0 D6), T8 counts down
to 0 and stops, T8_OUT toggles, the time-out status bit
(CTR0 D5) is set, and a time-out interrupt can be generat-
ed if it is enabled (CTR0 D1) (Figure 33). In Modulo-N
Mode, upon reaching terminal count, T8_OUT is toggled,
but no interrupt is generated. Then T8 loads a new count
(if the T8_OUT level now is 0), TC8L is loaded; if it is 1,
TC8H is loaded. T8 counts down to 0, toggles T8_OUT,
sets the time-out status bit (CTR0 D5) and generates an
interrupt if enabled (CTR0 D1) (Figure 34). This completes
one cycle. T8 then loads from TC8H or TC8L according to
the T8_OUT level, and repeats the cycle.
The user can modify the values in TC8H or TC8L at any
time. The new values take effect when they are loaded.
Care must be taken not to write these registers at the time
the values are to be loaded into the counter/timer, to en-
sure known operation. An initial count of 1 is not allowed (a
non-function will occur). An initial count of 0 will cause TC8
to count from 0 to %FF to %FE (Note, % is used for hexa-
decimal values). Transition from 0 to %FF is not a time-out
condition.
Note: Using the same instructions for stopping the
counter/timers and setting the status bits is not rec-
ommended. Two successive commands, first stopping
the counter/timers, then resetting the status bits is neces-
sary. This is required because it takes one counter/timer
clock interval for the initiated event to actually occur.
DS96LVO1100
PRELIMINARY
1-37
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