Renesas 7700 FAMILY, User Manual

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APPLICATIONS
7751 Group User’s Manual
17–37
17.1 Memory expansion
17.1.5 Example of I/O expansion
(1) Example of port expansion circuit using M66010FP
Figure 17.1.33 shows an example of a port expansion circuit using the M66010FP. Although Figure
17.1.33 is an expansion example in the high-speed running, when using 1.923 MHz or less frequency
for Serial I/O transfer clock, the same expansion is possible regardless of the bus cycle.
About Serial I/O control in this expansion example is described below.
In this example, 8-bit data transmission/reception is performed 3 times by using UART0 and 24-bit
port expansion is realized. Setting of UART0 is described below:
●
Clock synchronous serial I/O mode: Transmission/Reception enable state
●
Internal clock is selected. Transfer clock frequency is 1.66 MHz.
●
LSB first
The control process is described below:
➀
Output “L” level from port P4
5
. (Expansion I/O ports of M66010FP become floating state by this
signal. )
➁
Output “H” level from port P4
5
.
➂
Output “L” level from port P4
4
.
➃
Transmit/Receive 24-bit data by using UART0.
➄
Output “H” level from port P4
4
.
Figure 17.1.34 shows serial transfer timing between M37751 and M66010FP.