Manual

High-Speed Microcontroller User’s Guide
Rev: 062210 156 of 176
14. REAL-TIME CLOCK
The DS87C530 incorporates a real-time clock (RTC) onto the high-speed microcontroller family core.
This allows the device to perform real-time related functions such as data logging and timestamping
without an external timer. In addition, the RTC includes an alarm function that can execute a software
interrupt or resume operation from Stop mode at a specified time. The RTC features are controlled by 12
new SFRs. These registers as well as two new interrupt control bits are shown in Table 14-A
.
Table 14-A. Real-Time Clock Control and Status Bit Summary
NAME LOCATION FUNCTION RANGE RESET READ/WRITE ACCESS
ERTCI EIE.5 RTC Interrupt Enable 0 Unrestricted
PRTCI EIP.5 RTC Interrupt Priority 0 Unrestricted
RTASS.7–0 RTASS RTC Alarm Subsecond 0–FFh Unchanged Unrestricted
RTAS.5–0 RTAS RTC Alarm Second 0–3Bh Unchanged Unrestricted
RTAM.5–0 RTAM RTC Alarm Minute 0–3Bh Unchanged Unrestricted
RTAH.4–0 RTAH RTC Alarm Hour 0–17H Unchanged Unrestricted
RTCSS.7–0 RTCSS RTC Subsecond 0–FFh Unchanged
Read: only if RTCRE = 1.
Cannot be written. Cleared when
RTCWE 1 ≥ 0.
RTCS.5–0 RTCS RTC Second 0–3Bh Unchanged
RTCM.5–0 RTCM RTC Minute 0–3Bh Unchanged
RTCH.4–0 RTCH.4–0 RTC Hour 0–17h Unchanged
DOW.2–0 RTCH.7–5 RTC Day of Week 0–7h Unchanged
RTCD1.7–0
RTCD0.7–0
RTCD1, (MSB)
RTCD0
, (LSB)
RTC Day 0–FFFFh Unchanged
Read: only if RTCRE = 1.
Write: only if RTCWE = 1.
1.95ms Read/Write window
SRCE RTCC.7
RTC Subsecond
Compare Enable
Unchanged Unrestricted
SCE RTCC.6
RTC Second Compare
Enable
Unchanged Unrestricted
MCE RTCC.5
RTC Minute Compare
Enable
Unchanged Unrestricted
HCE RTCC.4
RTC Hour Compare
Enable
Unchanged Unrestricted
RTCRE RTCC.3 RTC Read Enable 0 Unrestricted
RTCWE RTCC.2 RTC Write Enable 0
Read: Unrestricted
Write: Timed Access
RTCIF RTCC.1 RTC Interrupt Flag Unchanged Unrestricted
RTCE RTCC.0 RTC Enable Unchanged
E4K TRIM.7
External 4096Hz RTC
Signal Enable
0
X12/6 TRIM.6
RTC Crystal
Capacitance Select
Unchanged
Read: Unrestricted
Write: Timed Access
TRM2–0
TRIM
.5
TRIM
.3
TRIM
.1
RTC Trim Bit 2–0 Unchanged
Read: Unrestricted
Write: Timed Access
The RTC control and status registers can be subdivided into four groups: RTC time registers
(RTCSS
;FAh, RTCS;FBh, RTCM;FCh, RTCH;FDh, RTCD0;FEh, RTCD1;FFh), RTC alarm registers
(RTASS
;F2h, RTAS;F3h, RTAM;F4h, RTAH;F5h), RTC calibration (TRIM;96h), and RTC control
(RTCC
;F9h).