R15UZ0002EU0100 Rev.1.00 Page 3
Oct 6, 2021
RTKA788152DE0000BU Evaluation Board Manual
1. Functional Description
1.1 Operational Characteristics
1.1.1 Driver Operation
A logic high at the driver enable pin (DE) activates the driver and causes the differential driver outputs (Y and Z) to
follow the logic states at the data input (DI). A logic high at DI causes Y to turn high and Z to turn low. In this case,
the differential output voltage, defined as VOD = VY– VZ, is positive. A logic low at DI reverses the output states
reverse, turning Y low and Z high, therefore, making VOD negative. A logic low at DE disables the driver, making Y
and Z high-impedance. In this condition, the logic state at DI is irrelevant. To ensure the driver remains disabled
after device power-up, Renesas recommends connecting DE through a 1kΩto 10kΩpull-down resistor to ground.
1.1.2 Receiver Operation
A logic low at the receiver enable pin (RE) activates the receiver and causes its output (RO) to follow the bus
voltage at the differential receiver inputs (A and B); the bus voltage is defined as VAB = VA- VB. For VAB ≥-0.05V,
RO turns high, and for VAB ≤-0.2V, RO turns low. For input voltages between -50mV and -200mV, the state of RO
is undetermined, and therefore can be high or low. A logic high at RE disables the receiver, making RO high-
impedance. In this condition, the polarity and magnitude of the input voltage is irrelevant. To ensure the receiver
output remains high when the receiver is disabled, Renesas recommends connecting RO, using a 1kΩto 10kΩ
pull-up resistor to VCC. To enable the receiver to immediately monitor the bus traffic after device power- up,
connect RE through a 1kΩto 10kΩpull-down resistor to ground.
Figure 2. Typical Operating Circuits of Half-Duplex and Full-Duplex Transceivers
Table 1. Driver Truth Table
Inputs Outputs
FunctionRE DE DI Y Z
X H H H L Actively drives bus high
X H L L H Actively drives bus low
L L X Z Z Driver disabled, outputs high-impedance
H L X Z Z Shutdown mode: driver and receiver disabled for more than 600ns
A
B
RO
DE
DI
R
D
RT
GND
VCC
RE
5V
10k
10k 10k
RL78
MCU Y
Z
100n
RB
(option al)
RB
(option al)
A/Y
B/Z
RO
DE
DI
R
D
RT
GND
VCC
RE
5V
10k
10k 10k
RL78
MCU
100n
RB
(option al)
RB
(option al)
