Chapter 3 Peripheral Control

■ 3.1 Peripheral control mode

The SH-2 can control peripherals via SMPC. There are the following two peripheral control methods.

(1) SMPC control mode

(2) SH-2 direct mode

◆ SMPC control mode

● Block diagram

Figure 3.1 shows a block diagram of SMPC control mode. SMPC control mode is activated by setting command parameters in the IREG of the SH-2 interface register and issuing the INTBACK command. The collection result of peripheral data is output to OREG as a result parameter.

Figure 3.1 Block diagram of SMPC control mode

● Features

It's a great way to minimize the overhead of accessing peripherals in your application.

● Settings for using SMPC control mode

Figure 3.2 shows an example configuration for using SMPC control mode.

Figure 3.2 shows an example configuration for port 1. The mode setting can be set independently for each port.

Figure 3.2 SMPC control mode setting example

● Default value of parallel I / O register when power is turned on

The parallel I / O registers when the power is turned on are set to the default values shown in Table 3.1.

Table 3.1 Default values of parallel I / O registers when power is turned on

Register name	Set value	Contents
IOSEL1 / 2	0H	SMPC control mode
EXL1 / 2	0H	PAD interrupt, VDP2 external latch disabled
DDR1 / 2	00H	All bit input

● How to use SMPC control mode

When acquiring peripheral data using the INTBACK command, the collected peripheral data is output to OREG as a result parameter. However, peripheral data can be more than the capacity of OREG. Therefore, in SMPC control mode, peripheral data collection is interrupted each time OREG is full. When OREG is full with peripheral data, SMPC raises an SMPC interrupt, requesting SH-2 to get the peripheral data.
Also, when peripheral data to be collected remains, the status register indicates that there is remaining data. After the SH-2 acquires the peripheral data, the SMPC resumes the peripheral data collection by requesting the SMPC to continue. You can also terminate the peripheral data collection by requesting a break when you do not need the remaining peripheral data. The above sequence is shown in Figure 3.3 and Figure 3.4.

・ Continue request

Continue from SH-2 to SMPC can be requested by inverting bit 7 of IREG0.

・ Break request

A break from SH-2 to SMPC can be requested by writing "1" to bit 6 of IREG0.

・ Notes on continue and break requests

Please note the conditions shown in Table 3.2 when requesting continue and break.

Table 3.2 Conditions for issuing Continue and Break

Request to issue		Reception conditions	SMPC operation
Continue	break
×	×	on hold	Waiting for request
×	○	break	Peripheral data collection interrupted, INTBACK command terminated
○	×	Continue	Continued peripheral data collection
○	○	Ban	No guarantee

-Termination condition of INTBACK command to acquire peripheral data

The INTBACK command for acquiring peripheral data ends under the following conditions.

(1) When all peripheral data collection is completed

(2) When peripheral data collection could not be completed by V-BLANK-IN (time over)

(3) When peripheral data collection is completed due to a break request from SH-2

Figure 3.3 All peripheral data acquisition sequence

Figure 3.4 Peripheral data acquisition cancellation sequence due to break request