Z80180/Z8S180/Z8L180
Enhanced Z180 Microprocessor
Zilog
CPU CONTROL REGISTER
CPU Control Register (CCR). This register controls the
and output drive/low noise options (Figure 31).
basic clock rate, certain aspects of Power-Down modes,
1
CPU Control Register (CCR)
D3
D0
D2 D1
D7 D6 D5 D4
Clock Divide
0 = XTAL/2
1 = XTAL/1
LNAD/DATA
0 = Standard Drive
1 = 33% Drive on
A19-A0, D7-D0
STANDBY/IDLE Enable
00 = No STANDBY
LNCPUCTL
0 = Standard Drive
1 = 33% Drive on CPU
Control Signals
01 = IDLE After SLEEP
10 = STANDBY After SLEEP
11 = STANDBY After SLEEP
64-Cycle Exit
LNIO
(QUICK RECOVERY)
0 = Standard Drive
1 = 33% Drive on
Group 1 I/O Signals
BREXT
0 = Ignore BUSREQ
on STANDBY/IDLE
1 = STANDBY/IDLE Exit
on BUSREQ
LNPHI
0 = Standard Drive
1 = 33% Drive on
PHI Pin
Figure 31. CPU Control Register (CCR) Address 1FH
Bit 7. Clock Divide Select. If this bit is 0, as it is after a Re-
When D6 and D3 are both 1, setting IOSTOP (ICR5) and
executing a SLP instruction puts the part into QUICK RE-
COVERY STANDBY mode, in which the on-chip oscillator
is stopped, and the part allows only 64 clock cycles for the
oscillator to stabilize when it's restarted.
set, the Z80180/Z8S180/Z8L180 divides the frequency on
the XTAL pin(s) by two to obtain its master clock PHI. If this
bit is programmed as 1, the part uses the XTAL frequency
as PHI without division.
If an external oscillator is used in divide-by-one mode, the
minimum pulse width requirement given in the AC Charac-
teristics must be satisfied.
The latter section, HALT and LoW POWER Modes, de-
scribes the subject more fully.
Bit 5 BREXT. This bit controls the ability of the
Z8S180/Z8L180 to honor a bus request during STANDBY
mode. If this bit is set to 1 and the part is in STANDBY
mode, a BUSREQ is honored after the clock stabilization
timer is timed out.
Bits 6 and 3. STANDBY/IDLE Control. When these bits
are both 0,
a
SLP instruction makes the
Z80180/Z8S180/Z8L180 enter SLEEP or SYSTEM STOP
mode, depending on the IOSTOP bit (ICR5).
When D6 is 0 and D3 is 1, setting the IOSTOP bit (ICR5)
Bit 4 LNPHI. This bit controls the drive capability on the
PHI Clock output. If this bit is set to 1, the PHI Clock output
will be reduced to 33 percent of its drive capability.
and
executing
a
SLP
instruction
puts
the
Z80180/Z8S180/Z8L180 into IDLE mode in which the on-
chip oscillator runs, but its output is blocked from the rest
of the part, including PHI out.
When D6 is 1 and D3 is 0, setting IOSTOP (ICR5) and ex-
ecuting a SLP instruction puts the part into STANDBY
mode, in which the on-chip oscillator is stopped and the
part allows 217 (128K) clock cycles for the oscillator to sta-
bilize when it's restarted.
DS971800401
P R E L I M I N A R Y
1-35
ZILOG [ ZILOG, INC. ]
