
DS87C530/DS83C530 EPROM/ROM Microcontrollers with Real-Time Clock
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Table 6. PMM Control and Status Bit Summary
NAME LOCATION FUNCTION RESET WRITE ACCESS
XT/ RG
EXIF.3
Control. XT/
RG =1, runs from crystal or external
clock; XT/
RG =0, runs from internal ring oscillator.
X
0 to 1 only when
XTUP = 1 and
XTOFF= 0
RGMD EXIF.2
Status. RGMD=1, CPU clock = ring; RGMD = 0,
CPU clock = crystal.
0 None
CD1, CD0 PMR7, PMR.6
Control. CD1, 0 = 01, 4 clocks; CS1, 0 = 10, PMM1;
CD1, 0 = 11, PMM2.
0, 1
Write CD1, 0 = 10 or
11 only from CD1, 0 =
01
SWB PMR.5
Control. SWB = 1, hardware invokes switchback to 4
clocks, SWB = 0, no hardware switchback.
0 Unrestricted
XTOFF PMR.3
Control. Disables crystal operation after ring is
selected.
0
1 only when XT/
RG
= 0
PIP STATUS.7
Status. 1 indicates a power-fail interrupt in service.
0 None
HIP STATUS.6
Status. 1 indicates high priority interrupt in service.
0 None
LIP STATUS.5
Status. 1 indicates low priority interrupt in service.
0 None
XTUP STATUS.4
Status. 1 indicates that the crystal has stabilized.
1 None
SPTA1 STATUS.3
Status. Serial transmission on serial port 1.
0 None
SPRA1 STATUS.2
Status. Serial word reception on serial port 1.
0 None
SPTA0 STATUS.1
Status. Serial transmission on serial port 0.
0 None
SPRA0 STATUS.0
Status. Serial word reception on serial port 0.
0 None
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