Z89175 Zilog., Z89175 Datasheet - Page 39

• Manufacturer Part Number: Z89175
• Description: Voice Processing Controllers
• Manufacturer: Zilog.

Zilog
Port Configuration Register (PCON). The PCON regis-
ter configures the comparator output on Port 3. The PCON
register (Figure 25) is located in the Expanded Register
File at Bank F, location 00H.
Comparator Output Port 3 (D0). Bit 0 controls the com-
parator use in Port 3. A 1 in this location brings the com-
parator outputs to P34 and P35, and a 0 releases the Port
to its standard I/O configuration.
Port 4 and 5 Configuration Register (P45CON). The
P45CON register configures Port 4 and Port 5, individual-
ly, to open-drain or push-pull active. This register is located
in the Expanded Register File at Bank F, location 06H (Fig-
ure 26).
Port 4 Open-Drain (D0). Port 4 can be configured as an
open-drain by resetting this bit (D0 = 0) or configured as
push-pull active by setting this bit (D0 = 1). The default val-
ue is 1.
Port 5 Open-Drain (D4). Port 5 can be configured as an
open-drain by resetting this bit (D4 = 0) or configured as
push-pull active by setting this bit (D4 = 1). The default val-
ue is 1.
DS97TAD0100
Note: Reset condition is 11111110
PCON (F) %00
D7 D6 D5 D4 D3 D2
Figure 25. Port Configuration Register (PCON)
D1 D0
R Always "1"
W 0 P34,P37 Standard output
R Always "1"
W No effect
1 P34,P37 Comparator output
P R E L I M I N A R Y
Power-On Reset (POR). A timer circuit clocked by a ded-
icated on-board RC oscillator is used for the Power-On Re-
set (POR) timer function. The POR time allows VCC and
the oscillator circuit to stabilize before instruction execu-
tion begins.
The POR timer circuit is a one-shot timer triggered by one
of three conditions:
1. Power fail to Power OK status;
2. Stop-Mode Recovery (if D5 of SMR=1);
3. WDT time-out.
The POR time is a nominal 5 ms. Bit 5 of the STOP mode
register determines whether the POR timer is bypassed af-
ter Stop-Mode Recovery (typical for external clock, RC/LC
oscillators).
HALT. HALT turns off the internal CPU clock, but not the
XTAL oscillation. The counter/timers and external inter-
rupts IRQ0, IRQ1, IRQ2, and IRQ3 remain active. The de-
vices are recovered by interrupts, either externally or inter-
nally generated.
STOP. This instruction turns off the internal clock and ex-
ternal crystal oscillation. It reduces the standby current to
20 A or less. The STOP mode is terminated by a reset
only, either by WDT time-out, POR, SMR, or external re-
set. This causes the processor to restart the application
program at address 000CH. In order to enter STOP (or
HALT) mode, it is necessary to first flush the instruction
pipeline to avoid suspending execution in mid-instruction.
To do this, the user must execute a NOP (opcode=FFH)
immediately before the appropriate Sleep instruction, i.e.,
FF
6F
FF
7F
NOP
STOP
NOP
HALT
Voice Processing Controllers
or
; clear the pipeline
; enter Stop mode
; clear the pipeline
; enter Halt mode
Z89175/Z89176
39
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