z86e54 ZiLOG Semiconductor, z86e54 Datasheet - Page 37

• Manufacturer Part Number: z86e54
• Description: Z8 512 Byte Otp Mcu
• Manufacturer: ZiLOG Semiconductor

PS020102-1003
Counter/Timer
Interrupts
T
IN
Clock
Logic
P31
There is one 8-bit programmable counter/timer (T1), driven by its own 6-bit pro-
grammable prescaler. The T1 prescaler is driven by internal or external clock
sources (Figure 16).
The 6-bit prescaler divide the input frequency of the clock source by any integer
number from 1 to 64. Each prescaler drives its counter, which decrements the
value (1 to 256) that is loaded into the counter. When both counter and prescaler
reach the end of count, a timer interrupt request IRQ5 (T1) is generated. The
counter can be programmed to start, stop, restart to continue, or restart from the
initial value. The counters are also programmed to stop upon reaching zero (SIN-
GLE-PASS mode) or to automatically reload the initial value and continue count-
ing (MODULO-N CONTINUOUS mode).
The counter, but not the prescaler, are read at any time without disturbing their
value or count mode. The clock source for T1 is user-definable and is either the
internal microprocessor clock divided by four, or an external signal input through
Port 3. The TIMER mode register configures the external timer input (P31) as an
external clock, a trigger input that is retriggerable or non-retriggerable, or used as
a gate input for the internal clock.
The Z8
maskable and prioritized (Figure 17). The sources are divided as follows: the fall-
ing edge of P31 (AN 1), P32 (AN2), P33 (REF), the rising edge of P32 (AN2), by
software, and one counter/timer. The Interrupt Mask Register globally or individu-
ally enables or disables the six interrupt requests (Interrupt Types, Sources, and
Vectors).
Internal Clock
Gated Clock
Triggered Clock
External Clock
4
®
features six interrupts from six different sources. These interrupts are
Figure 16.Counter/Timer Block Diagram
Write
Initial Value
Counter
Register
Down
PRE1
6-Bit
Write
Internal Data Bus
Initial Value
Register
Counter
Down
8-Bit
T1
Read
Current Value
Z8
Register
T1
®
512 Byte OTP MCU
IRQ5
Z86E54
31