AM8530H AMD [Advanced Micro Devices], AM8530H Datasheet - Page 99

• Manufacturer Part Number: AM8530H
• Description: Serial Communications Controller
• Manufacturer: AMD [Advanced Micro Devices]

Support Circuitry Programming
Generator Out
RX DPLL Out
TX DPLL Out
Baud Rate
SYNC
RTxC
TRxC
PCLK
Figure 5–1 shows a simplified schematic diagram of the circuitry used in the clock multi-
plexing. It shows the inputs to the multiplexer section as well as the various signal inver-
sions that occur in the paths to the outputs. Also shown are the edges used by the re-
ceiver, transmitter, BRG, and DPLL to sample or send data or otherwise change state.
For example, the receiver samples data on the falling edge, but since there is an inver-
sion in the clock path between the RTxC pin and the receiver, a rising edge of the RTxC
pin samples the data for the receiver.
5.2.4
Selection of the clock options may be done anywhere in the initialization sequence, but
the final values must be selected before the receiver, transmitter, BRG, or DPLL are en-
abled to prevent problems from arbitrarily narrow clock signals out of the multiplexers.
The same is true of the crystal oscillator, in that the output should be allowed to stabilize
before it is used as a clock source.
OSC
ECHO
Clock Programming
ECHO
OSC
Figure 5–1. Clock Multiplexer
DPLL
BRG
RX
TX
Receiver
Transmitter
DPLL
Baud Rate
Generator
AMD
5–5