Section 19
LPC Interface (LPC)
Rev. 1.00 Mar. 12, 2008 Page 743 of 1178
REJ09B0403-0100
19.4.6
LPC Interface Shutdown Function (LPCPD)
The LPC interface can be placed in the shutdown state according to the state of the
LPCPD
pin.
There are two kinds of LPC interface shutdown state: LPC hardware shutdown and LPC software
shutdown. The LPC hardware shutdown state is controlled by the
LPCPD
pin, while the LPC
software shutdown state is controlled by the SDWNB bit. In both states, the LPC interface enters
the reset state by itself, and is no longer affected by external signals other than the
LRESET
and
LPCPD
signals.
Placing the slave in sleep mode or software standby mode is effective in reducing current
dissipation in the shutdown state. If software standby mode is set, some means must be provided
for exiting software standby mode before clearing the shutdown state with the
LPCPD
signal.
If the SDWNE bit has been set to 1 beforehand, the LPC hardware shutdown state is entered at the
same time as the
LPCPD
signal falls, and prior preparation is not possible. If the LPC software
shutdown state is set by means of the SDWNB bit, on the other hand, the LPC software shutdown
state cannot be cleared at the same time as the rising edge of the
LPCPD
signal. Taking these
points into consideration, the following operating procedure uses a combination of LPC software
shutdown and LPC hardware shutdown.
1. Clear the SDWNE bit to 0.
2. Set the ERRIE bit to 1 and wait for an interrupt by the SDWN flag.
3. When an ERRI interrupt is generated by the SDWN flag, check the LPC interface internal
status flags and perform any necessary processing.
4. Set the SDWNB bit to 1 to set LPC software standby mode.
5. Set the SDWNE bit to 1 and make a transition to LPC hardware standby mode. The SDWNB
bit is cleared automatically.
6. Check the state of the
LPCPD
signal to make sure that the
LPCPD
signal has not risen during
steps 3 to 5. If the signal has risen, clear SDWNE to 0 to return to the state in step 1.
7. If software standby mode has been set, exit software standby mode by some means
independent of the LPC.
8. When a rising edge is detected in the
LPCPD
signal, the SDWNE bit is automatically cleared
to 0. If the slave has been placed in sleep mode, the mode is exited by means of
LRESET
signal input, on completion of the LPC transfer cycle, or by some other means.
Summary of Contents for H8S Family
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Page 70: ...Section 1 Overview Rev 1 00 Mar 12 2008 Page 22 of 1178 REJ09B0403 0100...
Page 108: ...Section 2 CPU Rev 1 00 Mar 12 2008 Page 60 of 1178 REJ09B0403 0100...
Page 116: ...Section 3 MCU Operating Modes Rev 1 00 Mar 12 2008 Page 68 of 1178 REJ09B0403 0100...
Page 152: ...Section 5 Interrupt Controller Rev 1 00 Mar 12 2008 Page 104 of 1178 REJ09B0403 0100...
Page 206: ...Section 6 Bus Controller BSC Rev 1 00 Mar 12 2008 Page 158 of 1178 REJ09B0403 0100...
Page 420: ...Section 9 14 Bit PWM Timer PWMX Rev 1 00 Mar 12 2008 Page 372 of 1178 REJ09B0403 0100...
Page 476: ...Section 12 Watchdog Timer WDT Rev 1 00 Mar 12 2008 Page 428 of 1178 REJ09B0403 0100...
Page 552: ...Section 14 CRC Operation Circuit CRC Rev 1 00 Mar 12 2008 Page 504 of 1178 REJ09B0403 0100...
Page 712: ...Section 18 I2 C Bus Interface IIC Rev 1 00 Mar 12 2008 Page 664 of 1178 REJ09B0403 0100...
Page 804: ...Section 19 LPC Interface LPC Rev 1 00 Mar 12 2008 Page 756 of 1178 REJ09B0403 0100...
Page 838: ...Section 20 Ethernet Controller EtherC Rev 1 00 Mar 12 2008 Page 790 of 1178 REJ09B0403 0100...
Page 964: ...Section 24 RAM Rev 1 00 Mar 12 2008 Page 916 of 1178 REJ09B0403 0100...
Page 1066: ...Section 25 Flash Memory Rev 1 00 Mar 12 2008 Page 1018 of 1178 REJ09B0403 0100...
Page 1098: ...Section 26 Boundary Scan JTAG Rev 1 00 Mar 12 2008 Page 1050 of 1178 REJ09B0403 0100...
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