EM78451AP EMC [ELAN Microelectronics Corp], EM78451AP Datasheet - Page 19

• Manufacturer Part Number: EM78451AP
• Description: 8-Bit Microcontroller
• Manufacturer: EMC [ELAN Microelectronics Corp]

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Product Specification (V1.2) 05.27.2004
(This specification is subject to change without further notice)
NOTE: Vdd = 5V, set up time period = 16.2ms ± 5%
4.3 TCC/WDT Presacler
4.4 I/O Ports
Vdd = 3V, set up time period = 18.0ms ± 5%
An 8-bit counter is available as prescaler for the TCC or WDT. The prescaler is
available for either the TCC or WDT at any given time, and the PAB bit of CONT
register is used to determine the prescaler assignment. The PSR0~PSR2 bits
determine the prescale ratio. The prescaler is cleared each time the instruction is
written to TCC under TCC mode. The WDT and prescaler, when assigned to WDT
mode, are cleared by the WDTC or SLEP instructions. Fig. 6 depicts the circuit diagram
of TCC/WDT.
The I/O registers, from Port 5 to Port 9, are bi-directional tri-state I/O ports. P60~P67,
P74~P75, and P90~P91 provide the internal pull-high. P60~P67, P74~P75, and
P90~P95 provide programmable wake-up function through software. P76~P77 can
have an open-drain output by software control. P80~P81 are the R-option pins which
are enabled by software. When the R-option function is used, it is recommended that
P80 and P81 should be used as output pins. During the R-option enabled state, P80
and P81 must be programmed as input pins. If an external resistor is connected to P80
(P81) for the R-option function, the current consumption, if necessary, should be taken
as an important factor in the applications for low power consideration.
The I/O ports can be defined as "input" or "output" pins by the I/O control registers
(IOC5~IOC9) under program control. The I/O registers and I/O control registers are
both readable and writable. The I/O interface circuit is shown in Fig. 7. Note that the
reading path source of input and output pins is different when reading the I/O port.
R1(TCC) is an 8-bit timer/counter. TCC will increase by one at every instruction
The watchdog timer is a free running on-chip RC oscillator. The WDT will keep
cycle (without the prescaler).
running even when 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 the normal
mode by software programming (if Code Option bit ENWDT is "1"). Refer to WDTE
bit of IOCE register. Without presacler, the WDT time-out period is approximately
18 ms1.
8-Bit Microcontroller
EM78451
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