cx28500 Mindspeed Technologies, cx28500 Datasheet - Page 156

• Manufacturer Part Number: cx28500
• Description: Cx28500 Multichannel Synchronous Communications Controller
• Manufacturer: Mindspeed Technologies

8.3.1
The transmit Buffer Descriptor contains a group of bits that specify the data to be transmitted after the end of a
transparent mode message. The bits are specified as follows:
•
•
•
8.3.1.1
Idle Code (IC) bit field selects one of a set of idle pad fill octets to be sent after the current message is transmitted
in the event the next message descriptor is unavailable (i.e., Host-owned) or inter-message pad fill is requested via
PADCNT. The default idle code in transparent mode is all 1s, a silent signal.
8.3.1.2
Pad Count (PADCNT) bit field specifies how many pad fill octets (selected by IC) are transmitted between
messages. PADCNT specifies the minimum number of pad fill octets plus one, as follows:
1. PADCNT = 0: One IC
2. PADCNT = 1: Two ICs
3. PADCNT = 2: Three ICs
4. etc...
8.3.1.3
When the ABORT field is non-zero in any CX28500-owned transmit buffer descriptor, CX28500 interprets this as a
request to end an in-progress message with the abort sequence. Abort sequence for Transparent mode is defined
to be a sequence of all 1s. The abort sequence is terminated only when a new CX28500-owned message
descriptor with a non-zero BLEN becomes available. In this case, CX28500 resynchronizes the start of the next
message transmission to the time slot marked as the first time slot on that channel.
If ABORT ≠ 0, and the prior buffer descriptor on that channel contained EOM = 1, (i.e., the previous buffer
descriptor ended a message), the abort command is simply ignored and CX28500 moves onto the next message
descriptor.
The Host can set EOM = 1 in any transmit buffer descriptor to separate this transparent mode “message” from the
next message, according to the IC and PADCNT bit fields. Unlike HDLC mode, the number of pad fill octets
transmitted equals PADCNT plus one and no flag characters are inserted.
8.3.2
Transmit events are informational in nature and require no recovery actions.
28500-DSH-002-C
Idle Code specification, IC
Inter-message Pad Fill Count, PADCNT
Send an Abort Sequence, ABORT
NOTE:
Message Configuration Bits–Transparent Mode
Idle Code
Inter-Message Pad Fill
Ending a Message with an Abort or Sending an Abort Sequence
Transmit Events
Message configuration bits are also used in HDLC mode, but their meaning is slightly
different. Refer to
Mindspeed Proprietary and Confidential
Mindspeed Technologies
Section
8.2.5.
®
Basic Operations
141