ATM Controller
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
39-23
The ATM commands are described in
Table 39-8
.
Table 39-8. ATM Commands
Command
ATM
Opcode
Description
TRANSMIT
ACTIVATE
CHANNEL
000
Activates the channel specified in COMM_CH by inserting its channel number into the
APC scheduling table at the location indicated by the service pointer. The channel most
recently inserted is the first to be chosen by the APC. This command can be issued only
after initializing the channel by preparing valid BDs and a TCT.
In ESAR mode, program COMM_CH2 with the internal address of the APC priority level
assigned to the channel number specified in COMM_CH. (Put the 16-bit address in the
lower-order halfword of COMM_CH2.)
The
TRANSMIT
ACTIVATE
CHANNEL
command can be issued at any time. TCT[ACT]
indicates the activation status of the channel.
TRANSMIT
DEACTIVATE
CHANNEL
001
Deactivates the channel specified in COMM_CH by extracting its assigned channel
number from its APC scheduling table. This command should not be issued before the
CP completes sending all the BDs associated with the current channel number. The
channel number’s TCT can be assigned to a different ATM channel only after this
command has taken effect, that is, when the status flag TCT[ACT] is cleared by the CP
and when the channel is no longer found in the PHYs transmit queue. Note that ACT is
cleared the next time the channel number is encountered in the APC scheduling table
(maximum latency of one full pass through the APC scheduling table).
STOP
TRANSMIT
(A
BORT
)
010
Instructs the transmitter to stop the channel specified in COMM_CH. Channels are
stopped on cell boundaries.
Transmission stops after the channel’s current cell is next scheduled by the APC. After
the current cell is sent, the BD is closed, a new entry to the interrupt queue is optionally
added for the channel, the BD pointer is advanced to the next BD, and the
channel-disabled flag TCT[CDIS] is set. For AAL5 channels, instead of the current cell,
an abort cell (a last cell with PTI[0] = 1 and zero length) is sent to terminate the current
frame.
After the
STOP
TRANSMIT
command is completed, the stopped channel is still scheduled
by the APC, but the channel number is not forwarded to the transmit queue, effectively
leaving a hole in the transmit cell stream.
Issue a
RESTART
TRANSMIT
command to restart the channel.
RESTART
TRANSMIT
011
Restarts transmissions following a
STOP
TRANSMIT
command. This command is used to
restart the channel number specified in COMM_CH at the current BD.
STOP
RECEIVE
100
Stops the receiver from receiving cells for the channel specified in COMM_CH. The
channel-disabled flag RCT[CDIS] is set, and the in-frame flag RCT[INF] is cleared. The
current buffer remains empty; that is, RBD_PTR (or PTP_BD_PTR for PTP
connections) is not advanced to the next BD.
Cells received for this channel number after the
STOP
RECEIVE
command executes are
discarded.
RESTART
RECEIVE
101
Restarts the receiver for the channel specified in COMM_CH. RCT[CDIS] is cleared,
and the receiver begins receiving cells into the data buffer pointed to by RBD_PTR (or
PTP_BD_PTR for PTP connections).
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