| 摘要 |
PURPOSE:To protect internal data in memory when a power source is disconnected, to dispense with the re-transfer of display data when the power source is applied again, and to carry out system start-up in high speed by enabling memory for display to be backed up. CONSTITUTION:A switch selection signal 17 to set a battery backup mode is supplied from a switch control circuit 15 to a switch circuit 9 by a user instruction. Thereby, a main power source monitoring circuit 22 detects the disconnection of a main power source 5, and the backup of memory set in the battery backup mode previously can be performed by a battery 6. When the backup for a CGRAM 1 and main memory 2 are performed, a status signal 25 to prohibit the re-transfer of the display data in a CGRAM 19 or an external memory device 20 to the CGRAM 1 when the power source is applied again is outputted to an MPU 14, and the system start-up can be carried out in high speed by prohibiting the transfer of the display data. |
