Z86L0808PSC View Datasheet(PDF) - Zilog
Part Name
Description
MFG CO.
'Z86L0808PSC' PDF : 26 Pages View PDF
Z86L04/L08
Z8 8-Bit Cost-Effective Microcontrollers
Zilog
FUNCTIONAL DESCRIPTION (Continued)
r7 r6 r5 r4
r3 r2 r1 r0
R253
(Register Pointer)
The upper nibble of the register file address
provided by the register pointer specifies
the active working-register group.
FF
Register Group F
F0
R15 to R0
7F
70
6F
60
5F
50
4F
40
3F
Specified Working
30
Register Group
2F
20
1F
Register Group 1
10
0F
Register Group 0
I/O Ports
00
The lower nibble
of the register
file address
provided by the
instruction points
to the specified
register.
R15 to R0
R15 to R4
R3 to R0
Figure 13. Register Pointer
Stack Pointer. The Z8 has an 8-bit Stack Pointer (R255)
used for the internal stack that resides within the 60 gen-
eral-purpose registers. It is set to 00Hex after any reset.
General-Purpose Registers (GPR). These registers are
undefined after the device is powered up. The registers
keep their last value after any reset, as long as the reset
occurs in the VCC voltage-specified operating range. Note:
Register R254 has been designated as a general-purpose
register. But is set to 00Hex after any reset.
Counter/Timer. There are two 8-bit programmable
counter/timers (T0 and T1), each driven by its 6-bit pro-
grammable prescaler. The T1 prescaler is driven by inter-
nal or external clock sources. (Figure 14).
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 has been loaded into the counter. When both counter
and prescaler reach the end of count, a timer interrupt re-
quest IRQ5 (T1 or IRQ4 (T0) 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 (Single-Pass
mode) or to automatically reload the initial value and con-
tinue counting (Modulo-N Continuous Mode).
The counters, 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 mi-
croprocessor clock divided by four, or an external signal in-
put through Port 3. The Timer Mode register configures the
external timer input (P31) as an external clock, a trigger in-
put that is retriggerable or non-retriggerable, or used as a
gate input for the internal clock.
16
PRELIMINARY
DS97LVO0901
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