Z87C33 Datasheet, PDF (21/72 Pages) Zilog, Inc. – CMOS Z8® MCU Consumer Controller Processor

Z87C33
CMOS Z8“ MCU Consumer Controller Processor
15
Note:
Register E0h-EFh is only accessed via working register and
indirect addressing modes.
Stack Pointer. The internal register file is used for the stack. An 8-bit Stack Pointer
(SPL) is used for the internal stack that resides within the 236 general-purpose
registers. Stack Pointer High (SPH) is used as a general-purpose register.
Note: SPH and SPL are set to 00h after any RESET or Stop-Mode
Recovery.
Counter/Timers. There are two 8-bit programmable counter/timers (T0–T1), each
driven by its own 6-bit programmable prescaler. The T1 prescaler is driven by
internal or external clock sources; however, the T0 prescaler is driven by the inter-
nal clock only (Figure 10).
The 6-bit prescalers can 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 the counter reaches the
end of the count, a timer interrupt request, IRQ4 (T0) or IRQ5 (T1), is generated.
The counters are programmed to START, STOP, restart to CONTINUE, or restart
from the initial value. The counters can also be programmed to STOP upon reach-
ing 0 (SINGLE-PASS mode) or to automatically reload the initial value and con-
tinue counting (MODULO–N CONTINUOUS mode).
The counters, but not the prescalers, 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 divide-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 nonretriggerable, or as a gate
input for the internal clock. The counter/timers are cascaded by connecting the T0
output to the input of T1. T_IN mode is enabled by setting PRE1 bit D1 to 0.
PS015601-1003