Features
• 4 Bits x 16 Words
• High Voltage Type (20V Rating)
• Independent Asynchronous Inputs and Outputs
• 3-State Outputs
• Expandable in Either Direction
• Status Indicators on Input and Output
• Reset Capability
• Standardized Symmetrical Output Characteristics
• 100% Tested for Quiescent Current at 20V
• 5V, 10V and 15V Parametric Ratings
• Maximum Input Current of 1A at 18V Over Full Package Temperature Range; 100nA at 18V and +25oC
• Noise Margin (Over Full Package/Temperature Range)
- 1V at VDD = 5V
- 2V at VDD = 10V
- 2.5V at VDD = 15V
• Meets All Requirements of JEDEC Tentative Standard
No. 13B, “Standard Specifications for Description of
‘B’ Series CMOS Devices”

Description
CD40105BMS is a low-power first-in-first-out (FIFO) “elastic”
storage register that can store 16 4-bit words. It is capable of
handling input and output data at different shifting rates. This
feature makes it particularly useful as a buffer between asynchronous systems.
Each word position in the register is clocked by a control flipflop, which stores a marker bit. A “1” signifies that the position’s data is filled and a “0” denotes a vacancy in that position. The control flip-flop detects the state of the preceding
flip-flop and communicates its own status to the succeeding
flip-flop. When a control flip-flop is in the “0” state and sees a
“1” in the preceding flip-flop, it generates a clock pulse that
transfers data from the preceding four data latches into its
own four data latches and resets the preceding flip-flop to
“0”. The first and last control flip-flops have buffered outputs.
Since all empty locations “bubble” automatically to the input
end, and all valid data ripple through to the output end, the
status of the first control flip-flop (DATA-IN READY) indicates
if the FIFO is full, and the status of the last flip-flop (DATAOUT READY) indicates if the FIFO contains data. As the
earliest data are removed from the bottom of the data stack
(the output end), all data entered later will automatically
propagate (ripple) toward the output.
Loading Data - Data can be entered whenever the DATA-IN
READY (DIR) flag is high, by a low to high transition on the
SHIFT-IN (SI) input. This input must go low momentarily
before the next word is accepted by the FIFO. The DIR flag
will go low momentarily, until that data have been transferred
to the second location. The flag will remain low when all 16-
word locations are filled with valid data, and further pulses
on the SI input will be ignored until DIR goes high.