em78p156n ELAN Microelectronics Corp, em78p156n Datasheet - Page 16

• Manufacturer Part Number: em78p156n
• Description: 8-bit Micro-controller
• Manufacturer: ELAN Microelectronics Corp

This specification is subject to change without prior notice.
4.4 I/O Ports
• The watchdog timer is a free running on-chip RC oscillator. The WDT will keep on running even when
The I/O registers, both Port 5 and Port 6, are bi-directional tri-state I/O ports. Port 6 can be pulled high
internally by software. In addition, Port 6 can also have open-drain output by software. Input status
change interrupt (or wake-up) function on Port 6. P50 ~ P52 and P60 ~ P63 pins can be pulled down by
software. Each I/O pin can be defined as "input" or "output" pin by the I/O control register (IOC5 ~ IOC6).
P50~P51 are the R-option pins enabled by setting the ROC bit in the IOCE register to 1. When the
CLK=Fosc/4 is used if CLK bit is "1". If TCC signal source comes from external clock input, TCC is
increased by 1 at every falling edge or rising edge of TCC pin.
the oscillator driver has been turned off (i.e. in sleep mode). During normal operation or sleep mode, a
WDT time-out (if enabled) will cause the device to reset. The WDT can be enabled or disabled any
time during normal mode by software programming. Refer to WDTE bit of IOCE register. Without
prescaler, the WDT time-out period is approximately 18 ms
1
<Note>: Vdd = 5V, set up time period = 16.8ms ± 30%
CLK(=Fosc/2 or Fosc/4)
TCC
Pin
(in IOCE)
Vdd = 3V, set up time period = 18ms ± 30%
WTE
TE
WDT
0
1
0
1
TS
PAB
M
M
Fig. 5 Block Diagram of TCC and WDT
U
X
U
X
1
0
16
PAB
M
U
X
WDT time-out
8-bit Counter
8-to-1 MUX
0
MUX
SYNC
2 cycles
1
TCC overflow interrupt
1
(default).
PSR0~PSR2
PAB
Data Bus
TCC (R1)
M
U
X
PAB
Initial
value
IOCA
EM78P156N
OTP ROM
07.29.2004 (V1.2)