NCR 5977-1000, Руководство пользователя

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Hardware Installation 3-26
Diagnostics
Note:
This section is not applicable to NCR 5977 Graphical displays.
The 5977 Customer Display has internal Power Up Diagnostics that occur soon after
power–up or if a Reset Display command is received from the host software.
When the hardware is powered down, all registers and memory are lost. No recovery is
possible.
The Power Up Diagnostics include the following tests:
• Microcontroller test
• External Memory Character test
• Display test
Microcontroller Test
Note:
This section is not applicable to NCR 5977 Graphical displays.
The 5977 performs an initialization process once power is applied. The MCU first detects
the presence of the USB signal VBUS. If VBUS is detected, the 5977 initializes using the
USB communications. If VBUS is not present, the 5977 initializes the RS232
communications.
After communications interface is established, the boot loader verifies if the MCU
Program Memory contains a valid firmware. This is done by computing the FW
checksum and compare it with a pre-installed checksum value (pre-installed checksum
is written by the ROM FLASHER/Factory Default Utility).
When a valid firmware is present on the Program memory, the boot loader transfers all
the functions to the core firmware.
Once the core firmware is in control of the device, an internal RAM check follows. RAM
test writes a value 55h to each RAM location. All RAM are written. After the write phase
is complete, a read phase begins to ensure the writes held. If an error is discovered,
testing stops and the firmware begins executing an infinite loop.
If RAM check passed, the MCU pulls the default code page from the external Flash
Memory to the RAM.