GE MAC 1200, Руководство по обслуживанию

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2-14 MAC
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1200 resting ECG analysis system Revision D
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2012250-095
Functional Description: PCB Control CS_CI
Keypad Interface
The keypad interface contains the control register for 8 keypad columns and the
receiving register for 7 keypad rows, and the control signals for the status LEDs:
LED_LIN , LED_BATT _, LED_START , and LED_STOP .
Using the matrix of 8 x 7, up to 56 keypads can be detected. Identification of the key
pressed is as follows.

The controller activates a column, activation is via low-level, then the row-
register is read to identify the pressed key by a low-level. This procedure is
repeated with the next column, till all columns have been activated.
Printhead Control
The printhead controller takes on the complete control of the 216-mm thermal
printhead with a line width of 200 mm.
The output rate to the printhead is 1000/second. The resolution in the Y-direction is
8 dots/mm, in the X-time axis up to 40 dots/mm.
Thermal Printhead Dot Control
The MPC855T prepares a complete dot column and sends it to the FIFO. An FPGA
reads out a complete column of the FIFO and generates the digital control signals for
the printhead, which are shifted in series.
The duration of heating a dot column is defined through the pulse width of the PWM
Signal HEAT that is generated from the FPGA too.
In addition, the duration of heating a dot column is influenced by the thermal
printhead monitoring.