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Command issue timing

SMPC executes internal tasks using V-BLANK-IN interrupts.
Therefore, it is prohibited to issue commands from V-BLANK-IN in 300μS period.
In addition, the INTBACK command used to acquire various statuses and peripheral data of SMPC has stricter timings than other commands. For details of the INTBACK command, refer to 2.4 Non-reset System Management Command and Chapter 3 Peripheral Control.

● Common issues for command issuance timing

As mentioned above, issuance of all commands is prohibited within 300μS from V-BLANK-IN.

● INTBACK command

INTBACK command starts peripheral data collection with V-BLANK-OUT. In order to start peripheral data collection with V-BLANK-OUT, issue it after V-BLANK-IN and after 300μS, but before V-BLANK-OUT.

Figure 2.5 shows the INTBACK command issuance timing.

The INTBACK command can be used in the following three ways.

(1) Get SMPC status only
(2) Acquire peripheral data following acquisition of SMPC status
(3) Get peripheral data only

(2) When acquiring peripheral data following acquisition of SMPC status, an SMPC interrupt is generated when the SMPC status is aligned with OREG, and a result parameter is requested from SH2. After SH2 requests to continue, the SMPC starts collecting peripheral data.

Therefore, when acquiring a continuation request after obtaining the SMPC status, it is necessary to issue an INTBACK command to request continuation so that the peripheral data collection can be started with V-BLANK-OUT.

In addition, SMPC status acquisition is completed in about 300μS after issuing the INTBACK command, and an SMPC interrupt is requested to SMPC.

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