Renesas Hitachi H8S/2191, Hardware Manual

Page: 262 / 1065

Rev. 2.0, 11/00, page 235 of 1037
Section 11 I/O Port
11.1 Overview
11.1.1 Port Functions
This LSI has seven 8-bit I/O ports (including one CMOS high-current port), one 4-bit I/O port,
and one 8-bit input port. Table 11.1 shows the functions of each port. Each I/O part a port
control register (PCR) that controls an input and output and a port data register (PDR) for storing
output data. The input and output can be controlled in a unit of bit. The pin whose peripheral
function is used both as an alternative function can set the pin function in a unit of bit by a port
mode register (PMR).
11.1.2 Port Input
(1) Reading a Port
•
When a general port of PCR = 0 (input) is read, the pin level is read.
•
When a general port of PCR = 1 (output) is read, the value of the corresponding PDR bit
is read.
•
When the pins (excluding AN7 to AN0 and RP7 to RP0 pins) set to the peripheral
function are read, the results are as given in items (1) and (2) according to the PCR value.
(2) Processing Input Pins
The general input port or general I/O port is gated by read signals. Unused pins can be left
open if they are not read. However, if an open pin is read, a feedthrough current may apply
during the read period according to an intermediate level. The read period is about one-state.
Relevant ports: P0, P1, P2, P3, P4, P5, P6, P7, P8
When an alternative pin is set to an alternative function other than the general I/O, always set
the pin level to a high or low level. If the pin is left open, a feedthrough current applies
according to an intermediate level, which adversely affects reliability, causes malfunctions,
and in the worst case may damage the pin.
Because the PMR is not initialized in low power consumption mode, pay attention to the pin
input level after the mode has been shifted to the low power consumption mode.
Relevant pins:
,&, ,54 to ,54, SCK1, SCK2, SI1, SI2, &6, FTIA, FTIB, FTIC, FTID,
TRIG, TMBI,
$'75*, EXCAP, EXTTRG