SyncMOS Technologies Inc.
May 2001
SM89516
SM89516 has 768 byte on-chip RAM which can be accessed by external memory addressing method only. (By
instruction MOVX). The address space of instruction MOVX @Rn is determined by bit 1 and bit 0 (RAMS1,
RAMS0) of RCON. The default setting of RAMS1, RAMS0 bits is 00 (page0).
RAMS1
0
0
1
RAMS0
0
1
0
MOVX @Ri i=0,1 mapping to expended RAM address
$0000 ~ $00FF
$0100 ~ $01FF
$0200 ~ $02FF
Port 4 for PLCC or QFP package:
The bit addressable port 4 is available with PLCC or QFP package. The port 4 has only 4 pins and its port
address is located at 0D8H. The function of port 4 is the same as the function of port 1, port 2 and port 3.
port4 (P4, $D8)
Unused
Reset
value
*
MSB
The bit 3, bit 2, bit 1, bit 0 output the setting to pin P4.3, P4.2, P4.1, P4.0 respectively.
Unused
*
Unused
*
Unused
*
P4.3
1
P4.2
1
P4.1
1
P4.0
1
LSB
Extension Function Description
Watch Dog Timer
The Watch Dog Timer (WDT) is a 16-bit free-running counter that generate reset signal if the counter overflows. The WDT
is useful for systems which are susceptible to noise, power glitches, or electronics discharge which causing software dead
loop or runaway. The WDT function can help user software recover form abnormal software condition. The WDT is different
from Timer0, Timer1 and Timer2 of general 8052. To prevent a WDT reset can be done by software periodically clearing
the WDT counter.
The SM89516 WDT has selectable divider input for the time base source clock. To select the divider input, the setting of
bit2~bit0 (PS2~PS0) OF Watch Dog Timer Control Register (WDTC) should be set accordingly.
The WDT is enable by setting 1 to the bit 7 (WDTE) of WDTC. After WDTE set to 1, the 16-bit counter starts to count with
the selected time base source clock which set by PS2~PS0. It will generate a reset signal when overflows. The WDTE bit
will be cleared to 0 automatically when SM89516 been reset, either hardware reset or WDT reset.
To reset the WDT is done by setting 1 to the bit 5 (CLEAR) of WDTC. This will clear the content of the 16-bit counter and let
the counter re-start to count from the beginning.
Specifications subject to change without notice,contact your sales representatives for the most recent information.
7/19
Ver 1.3
PID 89516 05/01
SYNCMOS [ SYNCMOS TECHNOLOGIES,INC ]
