GMS81C1404 Datasheet, PDF (37/93 Pages) Hynix Semiconductor – 8-BIT SINGLE-CHIP MICROCONTROLLERS

GMS81C1404/GMS81C1408
10. I/O PORTS
The GMS81C1404 and GMS81C1408 has four ports, RA,
RB, RC and RD. These ports pins may be multiplexed with
an alternate function for the peripheral features on the de-
vice. In general, when a initial reset state, all ports are used
as a general purpose input port.
All pins have data direction registers which can set these
ports as output or input. A “1” in the port direction register
defines the corresponding port pin as output. Conversely,
write “0” to the corresponding bit to specify as an input
pin. For example, to use the even numbered bit of RA as
output ports and the odd numbered bits as input ports, write
“55_H” to address C1_H (RA direction register) during initial
setting as shown in Figure 10-1 .
10.1 RA and RAIO registers
RA is an 8-bit bidirectional I/O port (address C0_H). Each
port can be set individually as input and output through the
RAIO register (address C1_H).
RA7~RA1 ports are multiplexed with Analog Input Port
(AN7~AN1) and RA0 port is multiplexed with Event
Counter Input Port (EC0).
RA Data Register
ADDRESS : C0H
RESET VALUE : Undefined
RA
RA7 RA6 RA5 RA4 RA3 RA2 RA1 RA0
RA Direction Register
RAIO
INPUT / OUTPUT DATA
ADDRESS : C1H
RESET VALUE : 00000000
DIRECTION SELECT
0 : INPUT PORT
1 : OUTPUT PORT
RA Function Selection Register
RAFUNC
ADDRESS : CAH
RESET VALUE : 00000000
ANSEL7 ANSEL6 ANSEL5 ANSEL4 ANSEL3 ANSEL2 ANSEL1 ANSEL0
0 : RA4
1 : AN4
0 : RA5
1 : AN5
0 : RA6
1 : AN6
0 : RA7
1 : AN7
0 : RB0
1 : AN0
0 : RA1
1 : AN1
0 : RA2
1 : AN2
0 : RA3
1 : AN3
Figure 10-2 Registers of Port RA
The control register RAFUNC (address CA_H) controls to
Reading data register reads the status of the pins whereas
writing to it will write to the port latch.
WRITE “55H” TO PORT RA DIRECTION REGISTER
C0H
C1H
C2H
C3H
RA DATA
RA DIRECTION
RB DATA
RB DIRECTION
01010101
7 6 5 4 3 2 1 0 BIT
IOIOIOIO
7 6 5 4 3 2 1 0 PORT
I: INPUT PORT
O: OUTPUT PORT
Figure 10-1 Example of port I/O assignment
select alternate function. After reset, this value is “0”, port
may be used as general I/O ports. To select alternate func-
tion such as Analog Input or External Event Counter Input,
write “1” to the corresponding bit of RAFUNC.Regardless
of the direction register RAIO, RAFUNC is selected to use
as alternate functions, port pin can be used as a correspond-
ing alternate features (RA0/EC0 is controlled by RB-
FUNC)
PORT
RAFUNC.7~0
Description
RA7/AN7
0
RA7 (Normal I/O Port)
1
AN7 (ADS2~0=111)
RA6/AN6
0
RA6 (Normal I/O Port)
1
AN6 (ADS2~0=110)
RA5/AN5
0
RA5 (Normal I/O Port)
1
AN5 (ADS2~0=101)
RA4/AN4
0
RA4 (Normal I/O Port)
1
AN4 (ADS2~0=100)
RA3/AN3
0
RA3 (Normal I/O Port)
1
AN3 (ADS2~0=011)
RA2/AN2
0
RA2 (Normal I/O Port)
1
AN2 (ADS2~0=010)
RA1/AN1
0
RA1 (Normal I/O Port)
1
AN1 (ADS2~0=001)
RA0/EC0¹
RA0 (Normal I/O Port)
EC0 (T0CK2~0=111)
1. This port is not an Analog Input port, but Event Counter clock
source input port. ECO is controlled by setting TOCK2~0 =
111. The bit RAFUNC.0 (ANSEL0) controls the RB0/AN0/AVref
port (Refer to Port RB).
June. 2001 Ver 1.2
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