York 00497VIP manual Service

Service

The BRAM (battery backed random access memory) is a memory device that contains a battery that preserves the data during power failures. It is a replaceable part. Refer to the YORK Renewal Parts List. It is located in socket location U52. The Micro stores the setpoints programmed by the Operator or Service Technician, History Data and other data that requires preservation, in this device. Also, the day of week, time of day and calendar date time-keeping are done here.

The keypad is a matrix of conductors arranged in rows and columns (ref. Fig. 45 & 46). There are 4 rows and 8 columns. When a key is pressed, the conductors are pressed together at that point, creating continuity between that row conductor and the column conductor. The Keypad is read by applying a logic low to a row while leaving +5VDC pullup on all the other rows. The Micro then reads the 8 columns. If any column has a logic low on it, the key corresponding to that coordinate (row, column) is being pressed. The Micro reads the entire Keypad by repeating this routine beginning with row 1 and ending with row 4. The entire Keypad is read every Program cycle. The Micro selects the MUX inputs (Microboard J7, J8, J9) for input to the A/D Converter by writing sequential addresses to the FPGA. The FPGA holds each address until a new one is received from the Micro. As each address is applied to the MUX, the input corresponding to that address is passed through the MUX to the A/D Converter. The A/D Converter will convert the analog value to a digital word when the Micro writes a “start conversion” pulse to the FPGA. The FPGA passes this to the A/D Converter. The Micro allows access to the PC-104 port (Microboard J16, J17) by writing an enable pulse to the FPGA. The FPGA applies this to the data transceiver, allowing data to be output to or input from the PC-104 Port.

To provide flexibility for future Analog Inputs (to Microboard J7), 2 analog inputs can be configured for either 0-10VDC or 4-20mA, Transducer or Thermistor inputs using Program Jumpers JP21 and JP22. The position of the jumper determines which type of input can be connected. Refer to Fig. 36 and Table 2, “Program Jumpers”.

These inputs are for future YORK Factory expansion use only. They are not general application spare inputs that will support arbitrarily installed devices. Devices CANNOT be connected to these inputs until the program has been modified to read and process the input. Unless YORK documentation shows a device connected to the input with a defined function, the input cannot be used.

The Microboard receives 2 supply voltages (Microboard J1) from the Power Supply; +12VDC, +5VDC and Ground. The +12VDC and +5VDC are input to Voltage Regulators to derive other regulated voltages. The +5VDC is input to a +3.3VDC regulator. The output is a 3.3VDC regulated voltage. The +12VDC is input to a 5VDC regulator. The output of this regulator powers only the Analog circuits. This includes the MUX, A/D converter, and Thermistors. As depicted on Fig. 33, these voltages can be monitored at Test Posts TP1 through TP6.

The Microboard is equipped with 5 Serial Data Ports (ref. Fig. 35). Connector J2 is shared with both COM 1 and COM 4B. Each Port is dedicated for a specific function as follows:

a. COM 1 (J2) - RS-232. Printer.

b. COM 2 (J13) - RS-232. Not Used.

c. COM 3 (J12) - RS-485. Chiller panel communica- tions .

d.COM 4 (4A-J11), (4B-J2) - This port is actually two ports. However, they cannot be used simultaneously; only one of these ports can be connected to a device at a time. The position of Microboard Program Jumper J27 determines which port can be used (refer to Table 2). COM 4A (J11) is an RS-485 port that is used for Multi-Unit Communications. COM 4B (J2) is an RS-232 port that is used for MicroGateway.

e.COM 5 (J15) – Not Used.

70 YORK INTERNATIONAL