PSB7238 SIEMENS [Siemens Semiconductor Group], PSB7238 Datasheet - Page 73

• Manufacturer Part Number: PSB7238
• Description: Joint Audio Decoder-Encoder - Multimode
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

PSB 7238
Functional Blocks
Each data byte is transmitted at least twice (only twice if the receiver is fast enough so
that the transmitter works at maximum speed), namely once when MX is 1, and once
when MX is 0 in the next frame. The only exception is the first byte, which is transmitted
in three consecutive frames (where MX = 1, 0, 0, respectively).
In order for the transmitter to recognize that the receiver has correctly acknowledged the
last byte, the interrupt status MEA is set after the received MR bit is received at 1 in two
consecutive frames (interrupt status different from MAB). The condition for generating
an MEA interrupt status is the recognition of a MR = 0, 1, 1 sequence when MXC = 0.
Figure 32
Figure 32 shows the general case, Figure 33 the maximum speed case.
Software Handling of Monitor Channel Reception
The receiver of the monitor channel is controlled via the MRE bit. As long as the MRE bit
is zero, no evaluation of the received MX bit is done. If the MRE bit is set to 1, then the
monitor channel hardware waits for a start of a monitor packet. When the start of a
packet is recognized with a monitor byte matching monitor receive address,
acknowledgement can be enabled by the software by setting the MR control bit MRC
to 1. The hardware performs acknowledgement by setting the transmitted MR bit to 0.
Semiconductor Group
73
Data Sheet 1998-07-01