Operational Description - Sharp MZ-5500 Tehnical Manual

13. RTC (Real Time Clock)
13-1. Operational description
As the real time clock is implemented in the MZ-5500/5600, it has the
circuit which is shown in Fig.2-13-1. The RPSC01 RTC is backed up by the
battery power to retain the clock and the data in the internal RAM during
power off. Apart of the RAM can be accessed by the user.
RP5~1
CSRrc - - - - d e s
OSe
OUT
- - - _ t \ I A &
r·
f-5V
löRD
t
Iöw~
I
r
t
l~
I
~
A3
- - - - '\ J{)tJ
S
D3
1-
l
oSc.
IN~
Ji
1 R -RT(
~""--------'
Fig.13-1 Real time clock circuit
°The RP5C01 in the figure is the LSl designed for the real time clock and it
has the features shown in the table.
Although the RP5C01 is accesseQ with the 1/0 address 220H to 22FH, th e s e tu r
time of lORD and lOWR is . delayed via the LS74 D-flipflop to create RD and
WR signals, because the read/write setup timing 1s rather slow.
•
Table 13-1 Features of the RPSC01
°4-bit bidirectional bus: DO - D3
°4-bit address . input: AO - A3
°Internal timer to keep time (hours, minutes, seconds), calendar (100
years, leap year, month, day, day of the week)
°Choice of the 24 hours and 12 hours (am, pm) modes
°All timer data expressed by the BCD notation
o±30 seconds adjusting function
°Possible battery backup
°lnternal 26 x 4-bit RAM
°Possible
outp~~
of the_ alarm siEnal or 16Hz/1Hz timing pulse
?7