Sharp MZ-5500 - Ac C E Ssing the RTC Internal RAH

13-2. Accessing the RTC internal RAM
Total 26 nibbles internal RAM are provided in the RP5C01 RTC for the Mode 10
and 11 as shown in Table 2-13-3, they are the battery backed up RAM, though
not so large in capacity . But, all RÄMs. for Mode 10 are reserved by the
~ystem and those Mode ~ 1 are user accessible.
Se~ the flowchart below for the accessing methode
[Ex.]
(1) Write
To write the 4-bit da ta 5H in the
STAAT
addre?s OA of Mode 11.
Select RAH block
Set mode register
(0, , 0
,
,0 , , 0
0
) -
(X, X,1,0)
OA (X ,x ,1,1)
SSUB:
Write data in RAM
NO
ESUB:
f
N
o
(2) Read
To read
STAAT
of
Mode
Select RAM block
Set mode register
, (D.,D.,D"Do)-(X,X,I,O)
OA (X,X,I,I)
Read RAM data
E N
*Nibble
NO
CALL SSUB
MOV DX,22AH
MOV AL,05H
OUT DX,AL
CAL L ESUß
HOV
IN
OR
OUT
RET
HOV
IN
AND
OUT
RET
DX,22DH
AL,DX
AL,03H
DX,AL
DX,22DH
AL,DX
AL,OCH
DX,AL
the
4-bit
data in the
11 and to store
it in
address
DL.
OA
CALL
HOV
IN
AND
MOV
CALL
SSUB
DX,22AH
AL,DX
AL,OFIl
DL,AL
ESUB
= 4 bits