
21145
Preliminary
 Datasheet
7
br_ad<7:0>/
<mdm<7:0>
I/O
107, 108, 
110, 111, 
114, 115, 
117, 118
NA
For the 176-pin 21145 only
:
During operation, when accessing the modem chipset 
(mdm_chip_sel is asserted), these pins are used as the 
modem data lines bits 7 through 0. When the modem is 
not accessed (mdm_chip_sel is deasserted), these pins 
are used as the expansion ROM address and data lines.
br_ce_l
O
104
NA
Expansion ROM or external register chip enable.
c_be_l<3:0>
I/O
41, 58, 75, 
91
33, 49, 60, 
75
Bits 0 through 3 of the bus command and byte enable 
lines. Bus command and byte enable are multiplexed on 
the same PCI pins.
During the address phase of the transaction, these 4 bits 
provide the bus command.
During the data phase, these 4 bits provide the byte 
enable. The byte enable determines which byte lines 
carry valid data.  For example, bit 0 applies to byte 0, and 
bit 3 applies to byte 3.
clkrun_l
I/O
O/D
102
86
PCI/CardBus clock run indication. The host system 
asserts this signal to indicate normal operation of the 
clock. The host system deasserts clkrun_l when the clock 
is going to be stopped or slowed down to a 
nonoperational frequency.
If the clock is needed by the 21145, the 21145 asserts 
clkrun_l, requesting normal clock operation to be 
maintained or restored. Otherwise, the 21145 allows the 
system to stop the clock. 
devsel_l
I/O
69
55
Device select is asserted by the target of the current bus 
access. When the 21145 is the initiator of the current bus 
access, it expects the target to assert devsel_l within 5 
bus cycles, confirming the access. If the target does not 
assert devsel_l within the required bus cycles, the 21145 
aborts the cycle. To meet the timing requirements, the 
21145 asserts this signal in a medium speed (within 2 bus 
cycles).
frame_l
I/O
59
50
The frame_l signal is driven by the bus master to indicate 
the beginning and duration of an access. The frame_l 
signal asserts to indicate the beginning of a bus 
transaction.  While frame_l is asserted, data transfers 
continue. The frame_l signal deasserts to indicate that the 
next data phase is the final data phase transaction.
gep<0>
I/O
123
100
This pin can be configured by software to be a general-
purpose pin that performs either input or output functions. 
This general-purpose pin can provide an interrupt when 
functioning as an input.
gep<1>/activ
I/O
124
101
This pin can be configured by software to be:
A general-purpose pin that performs either input or 
output functions. This general-purpose pin can 
provide an interrupt when functioning as an input.
A status pin that provides an LED that indicates 
either receive or transmit activity.
Table 1. Functional Description of 21145 Signals (Sheet 2 of 8)
Signal
Type
Pin 
Number, 
176-pin
Pin 
Number, 
144-pin
Description