w77e58 Winbond Electronics Corp America, w77e58 Datasheet - Page 23

• Manufacturer Part Number: w77e58
• Description: 8 Bit Microcontroller
• Manufacturer: Winbond Electronics Corp America

WS:
POWER MANAGEMENT REGISTER
CD1,CD0: Clock Divide Control. These bit selects the number of clocks required to generate one
SWB:
XTOFF: Crystal Oscillator Disable. Setting this bit disables the external crystal oscillator. This bit can
ALE0FF: This bit disables the expression of the ALE signal on the device pin during all on-board
DME0: This bit determines the on-chip MOVX SRAM to be enabled or disabled. Set this bit to 1 will
0 = ALE expression is enable;
Wait State Signal Enable. Setting this bit enables the WAIT signal on P4.0. The device will
sample the wait state control signal WAIT via P4.0 during MOVX instruction. This bit is time
access protected.
machine cycle. There are three modes including divide by 4, 64 or 1024. Switching between
modes must first go back devide by 4 mode. For instance, to go from 64 to 1024
clocks/machine cycle the device must first go from 64 to 4 clocks/machine cycle, and then
from 4 to 1024 clocks/machine cycle.
Switchback Enable. Setting this bit allows an enabled external interrupt or serial port activity
to force the CD1,CD0 to divide by 4 state (0,1). The device will switch modes at the start of
the jump to interrupt service routine while a external interrupt is enabled and actually
recongnized by microcontroller. While a serial port reception, the switchback occurs at the
start of the instruction following the falling edge of the start bit.
only be set to 1 while the microcontroller is operating from the RC oscillator. Clearing this bit
restarts the crystal oscillator, the XTUP (STATUS.4) bit will be set after crystal oscillator
warmed-up has completed.
program and data memory accesses. External memory accesses will automatically enable
ALE independent of ALEOFF.
enable the on-chip 1KB MOVX SRAM.
Bit:
Mnemonic: PMR
CD1
7
CD0
CD1,
0
0
1
1
6
CD0
0
1
0
1
1 = ALE expression is disable
SWB
5
- 23 -
clocks/machine cycle
Reserved
4
64
1024
4
-
XTOFF
3
Preliminary W77E58
Publication Release Date: March 1999
ALE-OFF
Address: C4h
2
1
-
Revision A1
DME0
0