HD64570 Datasheet, PDF (237/469 Pages) Hitachi Semiconductor – Serial Communications Adaptor

Transmission Encoding and Timing
NRZ-type codes: With NRZ-type encoding (NRZ or NRZI), all transitions in the transmit data on
the TXD line occur at falling edges of the transmit clock input or output on the TXC line. Receive
data is latched from the RXD line on rising edges of the receive clock input or output on the RXC
line. Figure 5.39 shows the timing.
One bit cell
Transmitting
device
TXC
TXD
Transmit
Receiving
device
RXD
Latched on rise of RXC
RXC
Figure 5.39 Transmit and Receive Timing for NRZ-Type Codes
FM-type codes: With FM-type encoding (FM0, FM1, or Manchester), transitions in the transmit
data occur at the beginning and center of the bit cells, as shown in figure 1.8. With FM0 and FM1,
transitions at the beginning of bit cells occur at the rising edges of the transmit clock input or
output on the TXC line. Transitions at the centers of bit cells occur at the falling edges of the
transmit clock. With Manchester, transitions at the beginning of bit cells occur at the falling edge
of the transmit clock input or output on the TXC line. Transitions at the centers of bit cells occur at
the rising edges of the transmit clock.
• (a) FM0 and FM1
• (b) Manchester
Figure 5.40 shows the timing.
Rev. 0, 07/98, page 221 of 453