Z86L0408PSC ZILOG [Zilog, Inc.], Z86L0408PSC Datasheet - Page 16

• Manufacturer Part Number: Z86L0408PSC
• Description: Z8 8-Bit Cost-Effective Microcontrollers
• Manufacturer: ZILOG [Zilog, Inc.]

FUNCTIONAL DESCRIPTION (Continued)
Z86L04/L08
Z8 8-Bit Cost-Effective Microcontrollers
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.
16
FF
F0
70
60
5F
50
40
30
20
1F
10
00
7F
6F
4F
3F
2F
0F
The upper nibble of the register file address
provided by the register pointer specifies
the active working-register group.
Figure 13. Register Pointer
r7 r6 r5 r4
Register Group 1
Register Group F
Specified Working
Register Group 0
Register Group
I/O Ports
r3 r2 r1 r0
R253
(Register Pointer)
The lower nibble
of the register
file address
provided by the
instruction points
to the specified
register.
R15 to R0
R15 to R0
R15 to R4
R3 to R0
P R E L I M I N A R Y
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 V
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.
CC
voltage-specified operating range. Note:
DS97LVO0901
Zilog