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.
External Memory Character Test
Note: This section is not applicable to NCR 5977 Graphical displays.
A separate checksum test is performed on the external Flash. A Character Set has its own checksum byte stored in a specific block of a SPI flash sector.
If an error is discovered, testingstops and the Flash status is noted and saved for host retrieval later using the Reset command. Any character set stored in the Flash is considered invalid and any command received attempting to switch to one of these character sets is treated as an invalid command and ignored.
Display Test
Note: This section is not applicable to NCR 5977 Graphical displays.
If the display is not connected to a host through a serial lines or USB, it runs an extra test that turns on all pixels on the display (character cells) for about four seconds. This permits a user to examine the display for any pixel failure, but doesn’t require him to execute this test on every power up. The unit does not have the capability to determine if the Display Test passed. Once diagnostic testing is completed, line states are returned to normal and the firmware branches to its idle routine.
The host is able to detect a Retail Display failure by detecting exception conditions on the RTS or Busy lines for at least three seconds.
Note: When the I/F receives a Reset command, only the Microcontroller Test and External Memory Test Character are executed. The Display Test is not executed.
