PEF2091 Siemens Semiconductor Group, PEF2091 Datasheet - Page 233

• Manufacturer Part Number: PEF2091
• Description: ICs for Communications(ISDN Echocancellation Circuit)
• Manufacturer: Siemens Semiconductor Group

PEB 2091
PEF 2091
Programming
6.5
Example for Monitor Channel Programming
Note 67: This chapter applies only in µP mode.
The example on page 234 illustrates the read-out of the transceiver’s identification
number (ID). It consists of the transmission of a two-byte message from the control unit
®
to the transceiver in IOM
-2 channel 0. The transceiver acknowledges the receipt by
returning a two-byte long message in the Monitor channel. The procedure is absolutely
identical for Monitor channel 1.
The P starts the transfer procedure after having confirmed that the Monitor channel is
inactive. The first byte of Monitor data is loaded into the transmit register MOX. Via the
Monitor Control Register MOCR Monitor interrupts are enabled and control of the MX-bit
is handed over to the IEC-Q. Then transmission of the first byte begins. The transceiver
core reacts to a low level of the MX-bit by reading and acknowledging the Monitor
channel byte automatically. On detection of the confirmation, the IEC-Q issues a Monitor
interrupt to inform the P that the next byte may be sent. Loading the second byte into
the transmit register results in an immediate transmission (timing is controlled by the
IEC-Q). The transceiver core receives the second byte in the same manner as before.
When transmission is completed, the transceiver core sends "End of Message" (MX-bit
high).
It is assumed that a Monitor command was sent that needs to be answered by the
transceiver core (e.g. read-out of a register). Therefore, the transceiver core commences
to issue a two-byte confirmation after an End-of-Message indication from the IEC-Q has
been detected. The IEC-Q notifies the P via interrupt when new Monitor data has been
received. The processor may then read and acknowledge the byte at a convenient
instant. When confirmation has been completed, the transceiver core sends "EOM". This
generates a corresponding interrupt in the IEC-Q. By setting the MR-bit to high, the
Monitor channel is inactive, the transmission is finished.
Semiconductor Group
233
Data Sheet 01.99