Z86L79 Datasheet, PDF (19/58 Pages) Zilog, Inc. – Low-Voltage Microcontroller

Zilog
Z86L79/80
Low-Voltage Microcontroller
FUNCTIONAL DESCRIPTION
The Z8 CCP^™ incorporates special functions to enhance External Data Memory. Not accessible using the 28-pin
the Z8's functionality in consumer and battery operated ap- Z86L79/80.
1
plications.
Expanded Register File. The register file has been ex-
Reset. The device is reset in one of the following condi- panded to allow for additional system control registers,
tions:
and for mapping of additional peripheral devices along
with I/O ports into the register address area. The Z8 regis-
s Power-On Reset
ter address space R0 through R15 has now been imple-
s Watch-Dog Timer
mented as 16 groups of 16 registers per group. These reg-
ister groups are known as the ERF (Expanded Register
s Stop-Mode Recovery Source
File). Bits 7-4 of register RP select the working register
group. Bits 3-0 of register RP select the expanded register
s Low Voltage Detection
group (Figure 15).
Program Memory. The Z86L7X addresses up to 4K and
8 Kbytes of internal program memory. (Figure 10). The first
12 bytes of program memory are reserved for the interrupt
vectors. These locations contain five 16-bit vectors that
correspond to the five available interrupts. Addresses 12
to 4K, and 8K (dependent on version) consist of on-chip
mask-programmed ROM.
The upper nibble of the register pointer (Figure 12) selects
which group of 16 bytes in the register file, out of the full
256, will be accessed. The lower nibble selects the ex-
panded register file bank and, in the case of the Z86L79/80
Banks F and D are implemented. A 0H in the lower nibble
will allow the normal register file to be addressed, but any
other value from 1H to FH will exchange the lower 16 reg-
isters in favor of an expanded register group of 16 regis-
ters.
8191
Location of
First Byte of
Instruction
Executed
After RESET
12
11
10
9
8
7
Interrupt
Vector
(Lower Byte) ⁶
5
4
Interrupt
Vector
(Upper Byte) ³
2
1
0
On-Chip
ROM
Reset Start Address
Reserved
Reserved
IRQ4
IRQ4
IRQ3
IRQ3
IRQ2
IRQ2
IRQ1
IRQ1
IRQ0
IRQ0
For example:
Z86L79/80: (See Figure 15)
R253 RP = 00H
R0 = Port 0
R1 = Port 1
R2 = Port 2
R3 = Port 3
But if:
R253 RP = 0DH
R0 = CTRL0
R1 = CTRL1
R2 = CTRL2
R3 = Reserved
The counter/timers are mapped into ERF group D. Access
is easily done using the following example:
LD RP, #0DH Select ERF D for access and register Bank
0 as the working register group
LDR0,#xx access CTRL0
LD1, #xx access CTRL1
LDRP, #7DH Select expanded register group(ERF) Bank
D for access and register Group 7 as the working regis-
ter Group.
Figure 14. Program Memory Map
LD R1, 2 CTRL2 → register 71H
PRELIMINARY
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