
MOTOROLA
MC68330 USER'S MANUAL
4-25
Y5–Y0 — Frequency Control Bits
The Y-bits, with a value from 0–63, control the modulus downcounter in the
synthesizer feedback loop, causing it to divide by the value of Y+1 (see the
equation for determining system frequency). Changing these bits requires a time
delay for the VCO to relock.
RSVD — Reserved
This bit is reserved for factory testing.
SLIMP — Limp Mode
1=A loss of input signal reference has been detected, and the VCO is running at
approximately one-half the maximum speed (affected by the X-bit in the SYNCR
register), determined from an internal voltage reference.
0=External input signal frequency is at VCO reference.
SLOCK — Synthesizer Lock
1=VCO has locked onto the desired frequency (or system clock is driven externally).
0=VCO is enabled, but has not yet locked.
RSTEN — Reset Enable
1=Loss of input signal causes a system reset.
0=Loss of input signal causes the VCO to operate at a nominal speed without
external reference (limp mode), and the device continues to operate at that speed.
STSIM — Stop Mode System Integration Clock
1=When LPSTOP is executed, the SIM40 clock is driven from the VCO.
0=When LPSTOP is executed, the SIM40 clock is driven from an external crystal or
oscillator, and the VCO is turned off to conserve power.
STEXT — Stop Mode External Clock
1=When the LPSTOP instruction is executed, the external clock pin (CLKOUT) is
driven from the SIM40 clock as determined by the STSIM bit.
0=When the LPSTOP instruction is executed, the external clock is held low to
conserve power.
4.3.4 Chip-Select Registers
The following paragraphs provide descriptions of the registers in the chip-select function,
and an example of how to program the registers.
4.3.4.1
BASE
ADDRESS
REGISTERS. There are four 32-bit base address
registers in the chip-select function, one for each chip-select signal.
Base Address 1
$044, $04C, $054, $05C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RESET
BA31 BA30 BA29 BA28
BA27 BA26 BA25 BA24
BA23 BA22 BA21 BA20 BA19 BA18 BA17 BA16
U
UU
U
UUUUU
UU
U
Supervisor Only
Base Address 2
$046, $04E, $056, $05E
00
RESET
UU
UUU
UU
U
15
14
13
12
11
10
98
76
5432
10
BA15
BA14 BA13 BA12 BA11 BA10
BA9
BA8
FC3
FC2
FC1
FC0
WP
FTE
NCS
V