PT7A6632 Datasheet, PDF (30/61 Pages) Pericom Semiconductor Corporation – PT7A6632 32-Channel HDLC Controller

Data Sheet
PT7A6632 32-Channel HDLC Controller
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
• Flexible Hyperchannel Configuring Byte (Optional)
The byte follows the FILL/MASK byte if any. It is used to
configure flexible hyperchannel. Bits 0 - 4 specify number of
a channel to be grouped into or removed from a hyperchannel.
Bits 6 and 7 is for hyperchannel enable and add/delete respec-
tively. See Table 10 for details.
Table 10
Bit 7 (E) Bit 6 (A)
Descr iption
0
x
Hyperchannel assignment remains
unchanged.
1
0
Delete channel number in bits 0-4
from hyperchannel.
1
1
Add channel number in bits 0-4 to
hyperchannel.
Data Length is used to specify flexible hyperchannel. When
Data Length = 0, 1 or 2, only normal channel process. When
Data Length > 2, there is hyperchannel process.
The channel map may be updated in one cycle of channel
counting. In flexible hyperchannel mode, the HCS0 and HCS1
should be set as “0 0”, otherwise the standard hyperchannel
will override the flexible hyperchannel.
• Partial Command Buffer
If the CPU can not make next buffer ready before the PT7A6632
completes data transmission of a channel, the CPU will reset
the CF/P bit to indicate that it is a Partial Command Buffer
(CF/P=0, CMND=1). In this case the PT7A6632 will read Next
Buffer Address and send a HDLC flag(s) or a non-HDLC octet
all-ones to fill the gap, then the PT7A6632 turns to a new
buffer chain as if it complete a normal buffer process by setting
the MPTY and CF/P bits.
The PT7A6632 sends out flags or all-ones until it is informed
to resume data transmission by the CPU again. One Partial
Command Buffer sends one flag or one all-ones byte, a chain
of Partial Command Buffer sends multiple flags or ones. The
Partial Command Buffer processing will not change the MODE
and FILL/MASK.
• Flexible Hyperchannel
The Flexible Hyperchannel mode allows the PT7A6632 to
group any number of 32 64kb/s channels into a hyperchannel.
The Data Length (>2) is read to decide the number of addi-
tional channels to be added to a hyperchannel. If a previously
activated channel is assigned to a flexible hyperchannel, it
will suspend the original buffer process, and the process will
be restored once the channel is released from the hyperchannel.
It may take one frame time. A channel can be assigned to one
hyperchannel only.
If a Partial Command Buffer is processed after a partial data
buffer, the HDLC ABORT or non-HDLC all-ones will be sent.
Minimum Number of Data Bytes in a Tx Buffer
For Transmit Data Buffers and Transmit Command Buffers,
minimum number of data bytes is required for buffer mainte-
nance and buffer transition. The minimum numbers depend on
the current buffer type and next buffer type. Refer to Figure 25.
Figure 25. Minimum Data Bytes for Transmit Buffer
Current Buffer
Current Buffer
Next
Buffer
Partial Data Buffer
(000)*
Complete Data
Buffer (001)*
3 Bytes
Partial Data
Buffer (000)*
6 Bytes
Complete Data Buffer
(001)*
Next
Buffer
Complete Data
Buffer (001)*
2 Bytes
Partial Data
Buffer (000)*
5 Bytes
Current Buffer
Next
Buffer
Command Buffer
(10x)*
Complete Data
Buffer (001)*
2 Bytes
Partial Data
Buffer (000)*
5 Bytes
Current Buffer
Any Buffer
(xxx)*
* Status Bits: CMND, MPTY, CF/P
PT019(05/02)
Next Buffer
Command
Buffer (10x)*
2 Bytes
Min. Data Bytes
30
Ver:2