DP83916 datasheet(42/96 Pages) NSC

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40 SONIC-16 Registers (Continued)

4312 General Purpose Timer

The SONIC-16 contains a 32-bit general-purpose watchdog

timer for timing user-definable events This timer is ac-

cessed by the user through two 16-bit readwrite registers

(WT1 and WT0) The lower count value is programmed

through the WT0 register and the upper count value is pro-

grammed through the WT1 register

These two registers are concatenated together to form the

complete 32-bit timer This timer clocked at

the Transmit

Clock (TXC) frequency counts down from its programmed

value and generates an interrupt if enabled (Interrupt Mask

when

rolls

over

from

0000

0000h

FFFF FFFFh When the counter rolls over it continues dec-

rementing unless explicitly stopped (setting the STP bit)

The timer is controlled by the ST (Start Timer) and STP

(Stop Timer) bits in the Command register A hardware or

software reset halts but does not clear the General Pur-

pose timer

WT1 (Upper Count Value)

WT0 (Lower Count Value)

4313 Silicon Revision Register

This is a 16-bit read only register It contains information on

the current revision of the SONIC-16 The initial silicon be-

gins at 0000h and subsequent revision will be incremented

by one

50 Bus Interface

SONIC-16 features a high speed non-multiplexed 23-bit ad-

dress and 16-bit data bus designed for a wide range of sys-

tem environments SONIC-16 contains an on-chip DMA and

supplies all the necessary signals for DMA operation With

23 address lines SONIC-16 can access a full 4 M-word ad-

dress space To accommodate different memory speeds

wait states can be added to the bus cycle by two methods

The memory subsystem can add wait states by simply with-

holding the appropriate handshake signals In addition the

SONIC-16 can be programmed (via the Data Configuration

The SONIC-16 is designed to interface to both the National

Intel and Motorola style buses To facilitate minimum chip

count designs and complete bus compatibility the user can

program the SONIC-16 for the following bus modes

NationalIntel bus operating in synchronous mode

NationalIntel bus operating in asynchronous mode

Motorola bus operating in synchronous mode

Motorola bus operating in asynchronous mode

The mode pin (BMODE) along with the SBUS bit in the Data

Configuration Register are used to select the bus mode

This section describes the SONIC-16’s pin signals provides

system interface examples

and describes the various

SONIC-16 bus operations

51 PIN CONFIGURATIONS

There are two user selectable pin configurations for SONIC-

16 to provide the proper interface signals for either the

NationalIntel or Motorola style buses The state of the

BMODE pin is used to define the pin configuration

Figure

5-1 shows the pin configuration when BMODEe1 (tied to

VCC) for the Motorola style bus Figure 5-2 shows the pin

configuration when BMODEe0 (tied to ground) for the Na-

tionalIntel style bus

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