PEB20321 Datasheet, PDF (158/366 Pages) Siemens Semiconductor Group – Multichannel Network Interface Controller for HDLC MUNICH32X

PEB 20321
PEF 20321
Local Bus Interface (LBI)
LHOLD
(Input)
LHLDA
(Output)
LBREQ
(Output)
LCSO
(Output)
Output Signals
(LRD, LWR)
ITD10353
Figure 63 External Bus Arbitration (Regaining the Bus)
The falling LBREQ edge marks the last moment for LBREQ to trigger the indicated
regain-sequence. Even if LBREQ is activated earlier the regain-sequence is initiated by
LHOLD going high. LBREQ and LHOLD are connected via an external arbitration
circuitry.
Note that LHOLD may also be deactivated without the EBC requesting the bus.
6.2.7 LBI Bus Arbitration
This section covers the LBI initialization when the MUNICH32X is operating in local bus
Master mode or Slave mode, and the operation of bus mode transfers from hold to active
state (and vice versa).
Note that bus master mode means that the device is driving the local bus and
performing bus cycles, and bus slave mode means that the EBC bus is in HOLD mode,
and that an external controller may read the LBI Mailbox registers.
On start-up, the MUNICH32X could be set to operate in LBI bus arbitration master mode
(LCONF.ABM = ‘1’) or LBI bus arbitration slave mode (LCONF.ABM = ‘0’). The
arbitration master mode is chosen if the device needs to output the LHLDA signal.
Note that LCONF.HDEN = ‘1’ allows responding to the arbitration signals, whereas
LCONF.HDEN = ‘0’ causes this device not to give up its bus. This function can also be
used by software or hardware during critical cycles.
6.2.7.1 Master/Slave Bus Arbitration
The master normally drives the LBI bus signals such as LALE (only in multiplexed
mode), LWR and LRD. The slave is defined to input the LBI bus control signals (LALE,
Data Sheet
158
2001-02-14