CMX635 查看數據表（PDF） - CML Microsystems Plc

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CMX635

ISDN Subscriber Processor

CML Microsystems Plc 

ISDN Subscriber Processor

CMX635

another transmit octet is required. The original data octet will be retransmitted continuously until

the transmit buffer is refreshed. Setting the ‘Tx EOF’ bit in the ‘Monitor Channel Control’ register

when the ‘Tx Buffer Empty’ status flag is asserted terminates the monitor frame.

Data is received in the selected monitor channel by reading from the ‘Monitor Channel Receive’

register when the ‘Rx Data Available’ flag is asserted. The ‘Rx EOF’ flag indicates the end of a

received IOM frame and the ‘Rx Abort’ flag indicates an error in reception.

The Command/Indicate channels provide a mechanism for passing “real time” layer-1 primitives

(CI0) and status flags (CI1) between IOM devices. Data written to the ‘CI Transmit’ registers will

be immediately reflected in the appropriate CI channel and will persist until the register data is

changed. The received CI channel is read from the ‘CI Receive’ registers and ‘New CI Data’ flags

indicate when two consecutive frames contain new and identical CI data.

The ‘CI0 Transmit’ register contains extra locations to enable an IOM Timing Request (TIM) to be

generated and to control the Bus Activation Request (BAC) bit in the TIC channel. The TIM is

used to request activation of the upstream IOM device and pulls the DU pin low from its

deactivated open-drain state.

When the CMX635 is configured as a timing master, the IOM bus can be deactivated by turning

off the DCL and FSC and placing the IOMTx pin in the open drain state. An IOM deactivation

sequence can be optionally invoked that ensures deactivation is not completed until 4 frames of

the primitive DC (Deactivate confirmation - 1111b) has been received in the CI0 channel from all

downstream devices.

The CMX635 implements a sub-set of the TIC bus control functions. The TIC bus allows layer-1

control of the D-channel from other IOM devices. The CMX635 enables control of the transmitted

BAC bit in NT applications when required by the U transceiver device but does not generate or

monitor TIC bus addresses. In TE mode the D-channel access function will automatically operate

the Stop/Go (S/G) bit to prevent other layer-1 devices from accessing the D-channel when

occupied by the CMX635. The received BAC bit is monitored to establish when other layer-1

devices require access to the D-channel.

The CMX635 can be configured to reverse its Tx and Rx pin directions in the IC channels and/or

the MON1 and CI1 channels. This feature is known as “bus reversal” and enables the CMX635,

when configured as a downstream IOM device, to communicate with other downstream IOM

devices.

© 2001 Consumer Microcircuits Limited

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