Characterization of NEC Single-chip Calculator Circuits - µPD946 Series

The DCM-50A Platform supports the Characterization of many Non-TI single-chip calculator circuits with up to 42-pin packages using the DCM-50A Playground DIL42 Adapter mounted on top of the DCM-50A PG Frame Carrier with the voltages V_SS and V_DD/V_GG set to the appropriate levels. The µPD946 Series requires the DCM50A Playground KBD123 Keyboard with Switch Matrix due to their segment scanning of the keyboard matrix.

µPD946

Device-under-Test:

Keyboard: The Royal RSC-40 makes use of a keyboard assembly with 24 plastic keys pushing small conductive carbon pills mounted in a large silicone rubber membrane against contacts etched on a double-sided phenolic PCB. The sliding switch for the Memory-Accumulate function of the calculator is directly wired to the Keyboard-PCB. All switches are arranged in a 10*4 matrix with 9 rows connected to the SA-SH and SDP Outputs (Segment Scan) and the columns connected to the NK, FK1, FK2 and LK Inputs (Keyboard Scan) of the µPD946 single-chip calculator circuit. The remaining row of the 10*4 matrix is connected directly to the positive supply voltage V_SS.

Keyboard Matrix of the Royal RSC-40:

Display: The Royal RSC-40 makes use of an 9-digit Itron DP95A low-voltage Vacuum Fluorescent Display (VFD) connected directly to the respective 9 Digit Outputs D1 to D9 and 8 Segment Outputs SA to SG and SDP of the µPD946 and biased to approximately -28 Volts.

Display Layout:

Display Fonts:

Keyboard Scanning: The µPD946 Series of single-chip calculator circuits utilizes nine segment outputs and the V_SS line to scan the keyboard. While scanning the display, every three digits a short pause is inserted and all segment outputs are briefly activated to detect key presses. The µPD946 inserts every three completed display scan cycles a short sequential scan cycle, even if no keypress was detected.

Only the necessary digit-driver outputs are activated, when displaying a "0." only D1 would be enabled. The provided recording shows first the moment the [2] key located in the keyboard scan matrix of segment output SB and keyboard input NK (K0) was registered while displaying "1.". The next recording is showing the short pause between two 3-digit keyboard scan cycles with all segments activated and six complete display scan cycles to show the sequential scan cycles.

Display scanning: Display scanning is performed in D1 → D4 → D7 → D2 → D5 → D8 → D3 → D6 → D9 direction at a rate of about 320 Hz. A short pause for parallel keyboard scanning is inserted every three digits:

µPD947

Device-under-Test:

Keyboard: The Royal 91K (Model UA122) makes use of a keyboard assembly with 24 spring-supported plastic keys pushing small fingers on stamped sheet-metal pieces against contacts etched on a single-sided phenolic PCB. Additionally includes the keyboard assembly two 2-position sliding switches for power, and auto-summation and one 3-position sliding switch for decimal point setting. All switches are arranged in a 10*4 matrix with 9 rows connected to the SA-SH and SDP Outputs (Segment Scan) and the columns connected to the NK, FK1, FK2 and LK Inputs (Keyboard Scan) of the µPD947 single-chip calculator circuit. The remaining row of the 10*4 matrix is connected directly to the positive supply voltage V_SS.

Keyboard Matrix of the Royal 91K (Model UA122):

Display: The Royal 91K (Model UA122) makes use of an 9-digit Futaba 9-ST-12 low-voltage Vacuum Fluorescent Display (VFD) connected directly to the respective 9 Digit Outputs D1 to D9 and 8 Segment Outputs SA to SG and SDP of the µPD947 and biased to approximately -28 Volts.

Display Layout:

Display Fonts:

Keyboard Scanning: The µPD946 Series of single-chip calculator circuits utilizes nine segment outputs and the V_SS line to scan the keyboard. While scanning the display, every three digits a short pause is inserted and all segment outputs are briefly activated to detect key presses. The µPD946 inserts every three completed display scan cycles a short sequential scan cycle, even if no keypress was detected. The µPD947 uses a modified approach because the 3-position sliding switch for the decimal point setting will always generate a keypress. The provided recording shows the moment the [2] key located in the keyboard scan matrix of segment output SB and keyboard input NK (K0) was registered while displaying '2.'.

Only the necessary digit-driver outputs are activated, when displaying a "0." only D1 would be enabled. The provided recordings are showing the short pause between two 3-digit keyboard scan cycles with all segments activated and a six complete display scan cycles to show the missing sequential scan cycles.

Display scanning: Display scanning is performed in D1 → D4 → D7 → D2 → D5 → D8 → D3 → D6 → D9 direction at a rate of about 320 Hz. A short pause for parallel keyboard scanning is inserted every three digits:

µPD278

Device-under-Test:

Keyboard: The Olympia CD44S makes use of a keyboard assembly with 24 plastic keys pushing small fingers on stamped sheet-metal pieces against contacts etched on a single-sided phenolic PCB. The sliding power switch of the calculator is integrated on the Keyboard-PCB, too. All switches are arranged in a 10*3 matrix with 9 rows connected to the SA-SH and SDP Outputs (Segment Scan) and the columns connected to the NK, FK1 and FK2 Inputs (Keyboard Scan) of the µPD278 single-chip calculator circuit. The remaining row of the 10*3 matrix is connected directly to the positive supply voltage V_SS.

Keyboard Matrix of the Olympia CD44S:

Display: The Olympia CD44S makes use of an 9-digit Futaba 9-ST-10 low-voltage Vacuum Fluorescent Display (VFD) connected directly to the respective 9 Digit Outputs D1 to D9 and 8 Segment Outputs SA to SG and SDP of the µPD278 and biased to approximately -28 Volts.

Display Layout:

Display Fonts:

Keyboard Scanning: The µPD278 single-chip calculator circuit utilizes nine segment outputs and the V_SS line to scan the keyboard. While scanning the display, every three digits a short pause is inserted and all segment outputs are briefly activated to detect key presses.

Only the necessary digit-driver outputs are activated, when displaying a "0." only D1 would be enabled. The provided recording shows the moment the [2] key located in the keyboard scan matrix of segment output SB and keyboard input NK (K0 was registered while displaying '2.'.

Display scanning: Display scanning is performed in D1 → D4 → D7 → D2 → D5 → D8 → D3 → D6 → D9 direction at a rate of about 320 Hz. A short pause for parallel keyboard scanning is inserted every three digits: