h8s-2172 Renesas Electronics Corporation., h8s-2172 Datasheet - Page 393

• Manufacturer Part Number: h8s-2172
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family H8s-2100 Series
• Manufacturer: Renesas Electronics Corporation.

4. Clearing Suspend Signal Output Mask
5. USB Suspend Interrupt (USBI2)
6. Suspend Signal Output Mask
12.7.2
In the firmware mainly for the USB, if the USB enters suspend mode, this LSI enters software
standby mode which is the power-down state because power consumption of the system can be
reduced. Since the system clock (φ) is stopped in software standby mode, the suspend recover
interrupt (SUSRI) is used to recover from software standby mode.
Figure 12.17 shows the enter/recover sequence of suspend mode and software standby mode. And
the following 1 to 8 descriptions explain the operation at its each point.
To prevent access to the USB module by the CPU or DMAC from occurring in the interrupt
processing routine, the USUSOUT bit in USBSUSP is set to 1 after the setting such as to stop
the DMAC is made. Then output of the USSUSP pin goes low and the USCLK input from the
external transceiver is stopped.
After the USCLK input is stopped, do not access the USB module registers by the CPU or
DMAC.
Even if the USCLK is stopped, the internal suspend signal is negated after the USB bus state is
recovered from the suspend state.
Since the USBI2 interrupt is requested when the internal suspend signal is changed, if
interrupts are enabled, an interrupt is requested to the CPU even when the internal suspend
signal is negated.
In the interrupt processing routine, output of the USSUSP pin should be masked (fixed to 1) by
clearing the USUSOUT bit in USBSUSP to 0.
Then access to the USB module registers can be performed by the CPU or DMAC.
Software Standby in Suspend Mode
Rev. 2.00, 03/04, page 361 of 534