TMP47C101/201
3. Peripheral Hardware Function
3.1 Ports
The data transfer with the external circuit and the command/
status/data transfer with the internal circuit are performed by
using the I/O instructions (13 kinds). There are 4 types of ports:
I/O port
; Data transfer with external cir-
cuit
Command register ; Control of internal circuit
Status register
; Reading the status signal from
internal circuit
Data register
; Data transfer with internal cir-
cuit
These ports are assigned with port addresses (00H
through IFH). Each port is selected by specifying its port ad-
dress in an I/O instruction. Table 3-1 lists the port address as-
signments and the I/O instructions that can access the ports.
3.1.1 I/O Timing
(1) Input timing
External data is read from an input port or an I/O port
in the S3 state of the second instruction cycle during
the input instruction (2-cycle instruction) execution.
This timing cannot be recognized from the outside, so
that the transient input such as chattering must be
processed by program.
Figure 3-1. Input Timing
(2) Output timing
Data is output to an output port or an I/O port in the S4
state of the second instruction cycle during the output
instruction (2-cycle instruction) execution.
Figure 3-2. Output Timing
3.1.2 I/O Ports
The 47C101/201 have 4 I/O ports (11 pins) each as follows:
R4, R5
R8
; 4-bit input/output
; 2-bit input/output (shared with
external interrupt input and
timer/counter input)
KE
; 1-bit sense input (shared with
hold request/release signal in-
put)
Each output port contains a latch, which holds the out-
put data. The input ports have no latch; therefore, it is
desired to hold data externally until it is read or read
twice or more before processing it.
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