M16C28 Datasheet, PDF (303/423 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/Tiny SERIES

M16C/28 Group (M16C/28, M16C/28B)
17. Programmable I/O Ports
17.5 Pin Assignment Control Register (PACR)
Figure 17.10 shows the PACR register. After reset, set bits PACR2 to PACR0 in the PACR register before
a signal is input or output to each pin. When bits PACR2 to PACR0 are not set, some pins do not function
as I/O ports.
Bits PACR2 to PACR0: control pins to be used
Value after reset: 0002.
To select the 80-pin package, set the bits to 0112.
To select the 64-pin package, set the bits to 0102.
U1MAP bit: controls pin assignments for the UART1 function.
To assign the UART1 function to P64/CTS1/RTS1, P65/CLK1, P66/RxD1, and P67/TxD1, set the U1MAP
bit to 0 (P67 to P64).
To assign the function to P70/CTS1/RTS1, P71/CLK1, P72/RxD1, and P73/TxD1, set the U1MAP bit to 1
(P73 to P70)
The PRC2 bit in the PRCR protects the PACR register. Set the PACR register after setting the PRC2 bit in
the PRCR register.
17.6 Digital Debounce Function
Two digital debounce function circuits are provided. Level is determined when level is held, after applying
either a falling edge or rising edge to the pin, longer than the programmed filter width time. This enables
noise reduction.
________
_______ _____
This function is assigned to INT5/INPC17 and NMI/SD. Digital filter width is set in the NDDR register and
the P17DDR register respectively. Figure 17.11 shows the NDDR register and the P17DDR register.
Additionally, a digital debounce function is disabled to the port P17 input and the port P85 input.
Filter width : (n+1) x 1/f8 n: count value set in the NDDR register and P17DDR register
The NDDR register and the P17DDR register decrement count value with f8 as the count source. The
NDDR register and the P17DDR register indicate count time. Count value is reloaded if a falling edge or a
rising edge is applied to the pin.
The NDDR register and the P17DDR register can be set 0016 to FF16 when using the digital debounce
function. Setting to FF16 disables the digital filter. See Figure 17.12 for details.
Rev. 2.00 Jan. 31, 2007 ^{page 283} of 385
REJ09B0047-0200