CS89712 datasheet(10/170 Pages) CIRRUS

10 / 170 page

CS89712

DS502PP2

When both KBWEN and INTMR2 bit 0 are low,

the device can be awakened only by the external

WAKEUP pin or another enabled interrupt source.

The keyboard interrupt capability allows use of a

polled and/or interrupt-driven keyboard routine.

Notes:The keyboard interrupt is NOT deglitched.

2.2.4

Ethernet Port Software Suspend

The Ethernet port power features work in a differ-

ent manner than detailed above. Suspend mode-

may be entered via software. During this mode, all

internal Ethernet circuits are shut off except the I/O

Base Address register (Ethernet Port offset address

0020h) and the SelfCTL register.

To enter Suspend mode, the SWSuspend bit (Self-

CTL Register, bit 8) is set. To exit SW Suspend,

software must write to the CS89712 Ethernet (used

only to wake the Ethernet port, the Write data is ig-

nored). Upon exit, the CS89712 Ethernet performs

a complete reset, and then goes through a normal

initialization procedure.

2.3 Power-Up Sequence

The following sequence should be followed to en-

sure proper start up. If any of the timing sequences

recommended below are violated, then the part

may not start up properly, requiring a hard reset to

recover.

1) Upon power, the signal nPOR must be held ac-

tive (LOW) for a minimum of 100us, after VDD

has become settled.

2) After nPOR goes HIGH, the CS89712 will en-

ter the Standby State (and only this state). In

this state, the PLL and CPU are not enabled.

The only method that can be used to allow the

CS89712 to exit the Standby State into the Op-

erating State is by the WAKEUP signal going

active (HIGH).

Note:

It is not a requirement to use the nURESET

signal. If not used, the nURESET signal

must be HIGH, and it must have gone

HIGH prior to nPOR going HIGH. This is

due to the fact that nURESET is latched

into the device by the rising edge of nPOR.

When nURESET is LOW on the rising edge

of nPOR, it can force the device into one of

its Test Mode states.

3) After nPOR goes HIGH, the WAKEUP signal

cannot be detected as going HIGH, until after at

least two seconds. After two seconds, the

WAKEUP signal can become active, and it

must be HIGH for at least 125 us.

4) Before the WAKEUP signal is detected inter-

nally, it must go through a deglitching circuit.

This is why is must be active for at least 125us.

Then the PLL gets enabled. WAKEUP is ig-

nored immediately after waking up the system.

It also ignores it while in the Idle or Operating

State. It can constantly toggle with no affect on

the device. It will only be read again if nPOR

goes low and then high again, or if software has

forced the device back into the Standby State.

5) A maximum of 250 msec will pass before the

CPU starts to fetch the first instruction.

2.4 Resets

There are three asynchronous resets to the

CS89712: nPOR (Power On Reset), nPWRFL, and

nURESET. If any of these are active, a system reset

is generated internally. This will reset all internal

registers in the CS89712 except the RTC data and

match registers. These registers are only cleared by

nPOR allowing the system time to be preserved

through a user reset or power fail condition.

NOTE: The Ethernet Port has different reset conditions

and considerations than described in this sec-

tion. Refer to the following section for resetting

the Ethernet Port.

Any reset will also reset the CPU and cause it to

start execution at the reset vector when the

CS89712 returns to the Operating State.

Three signals are used to internally reset storage el-

ements. These are nPOR, nSYSRES (System Re-

set) and nSTBY. nPOR is an external signal.

nSTBY is equivalent to the external RUN signal.

CS89712 データシート(PDF) 10 Page - Cirrus Logic

CS89712 データシート(HTML) 10 Page - Cirrus Logic

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

データシートダウンロード