74F552 Datasheet, PDF (3/8 Pages) NXP Semiconductors – Octal registered transceiver with parity and flags 3-State

Functional Description
Data applied to the A-inputs are entered and stored in the
R register on the rising edge of the CPR Clock Pulse, pro-
vided that the Clock Enable (CER) is LOW; simultaneously,
the status flip-flop is set and the flag (FR) output goes
HIGH. As the Clock Enable (CER) returns to HIGH, the
data will be held in the R register. These data entered from
the A-inputs will appear at the B Port I/O pins after the Out-
put Enable (OEBR) has gone LOW. When OEBR is LOW,
a parity bit appears at the PARITY pin, which will be set
HIGH when there is an even number of 1s or all 0s at the Q
outputs of the R register. After the data is assimilated, the
receiving system clears the flag FR by changing the signal
at the OEBR pin from LOW-to-HIGH.
Data flow from B-to-A proceeds in the same manner
described for A-to-B flow. A LOW at the CES pin and a
LOW-to-HIGH transition at CPS pin enters the B-input data
and the parity-input data into the S registers and the parity
register respectively and set the flag output FS to HIGH. A
LOW signal at the OEAS pin enables the A Port I/O pins
and a LOW-to-HIGH transition of the OEAS signal clears
the FS flag. When OEAS is LOW, the parity check output
ERROR will be HIGH if there is an odd number of 1s at the
Q outputs of the S registers and the parity register. The flag
FS can be cleared by a LOW-to-HIGH transition of the
OEAS signal.
Register Function Table
(Applies to R or S Register)
Inputs
D
CP
CE
Internal
Q
Function
X
L
H
^X
H
L
L
NC Hold Data
L
Load Data
H
X
†
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
L
NC Keep Old Data
 = LOW-to-HIGH Transition
† = Not LOW-to-HIGH Transition
NC = No Change
Flag Flip-Flop Function Table
(Applies to R or S Flag Flip-Flop)
Inputs
Flag
CE
CP
OE Output
Function
H
L
^X
X
X
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
†
NC Hold Flag
^†
H Set Flag
L Clear Flag
 = LOW-to-HIGH Transition
† = Not LOW-to-HIGH Transition
NC = No Change
Output Control
OE
Internal A or B
Q
Outputs
Function
H
X
Z
Disable Output
L
L
L
Enable Output
L
H
H
Enable Output
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
Z = High Impedance
Parity Check Function
Parity Generation Function
Number of HIGHs in the
OEBR
Q Outputs of the R Register
H
X
L
0, 2, 4, 6, 8
L
1, 3, 5, 7
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
Z = High Impedance
Parity Output
Z
H
L
H = HIGH Voltage Level
L = LOW Voltage Level
X = Immaterial
OEAS
H
L
L
L
L
Number of HIGHs in
the Q Outputs of the S Register
X
0, 2, 4, 6, 8
1, 3, 5, 7
0, 2, 4, 6, 8
1, 3, 5, 7
Parity
Input
X
L
L
H
H
ERROR
Output
H
L
H
H
L
3
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