Philips Semiconductors

Objective specification

PDI1394P21

3-port physical layer interface

1999 Jul 09

19

18.0

PRINCIPLES OF OPERATION

The PDI1394P21 is designed to operate with an LLC such as the

Philips Semiconductors PDI1394L11 or PDI1394L21. The following

paragraphs describe the operation of the PHY-LLC interface.

The interface to the LLC consists of the SYSCLK, CTL0–CTL1,

D0–D7, LREQ, LPS, C/LKON, and /ISO terminals on the

PDI1394P21 as shown in Figure 9.

LINK LAYER

CONTROLLER

PDI1394P21

SYSCLK

CTL0–CTL1

D0–D7

LREQ

LPS

C/LKON

/ISO

/ISO

/ISO

SV01757

Figure 9.

PHY-LLC interface

The SYSCLK terminal provides a 49.152 MHz interface clock. all

control and data signals are synchronized to, and sampled on, the

rising edge of SYSCLK.

The CTL0 and CTL1 terminals form a bidirectional control bus,

which controls the flow of information and data between the

PDI1394P21 and LLC.

The D0–D7 terminals form a bidirectional data bus, which is used to

transfer status information, control information, or packet data

between the devices. The PDI1394P21 supports S100, S200, and

S400 data transfers over the D0–D7 data bus. In S100 operation

only the D0 and D1 terminals are used; in S200 operation only the

D0–D3 terminals are used; and in S400 operation all D0–D7

terminals are used for data transfer. When the PDI1394P21 is in

control of the D0–D7 bus, unused Dn terminals are driven low during

S100 and S200 operations. When the LLC is in control of the D0–D7

bus, unused Dn terminals are ignored by the PDI1394P21.

The LREQ terminal is controlled by the LLC to send serial service

requests to the PHY in order to request access to the serial bus for

packet transmission, read or write PHY registers, or control

arbitration acceleration.

The LPS and C/LKON terminals are used for power management of

the PHY and LLC. The LPS terminal indicates the power status of

the LLC, and may be used to reset the PHY-LLC interface or to

disable SYSCLK. The C/LKON terminal is used to send a wake-up

notification to the LLC and to indicate an interrupt to the LLC when

either LPS is inactive or the PHY register L bit is zero.

The /ISO terminal is used to enable the output differentiation logic

on the CTL0–CTL1 and D0–D7 terminals. Output differentiation is

required when an isolation barrier of the type described in Annex J

of IEEE Std 1394-1995 is implemented between the PHY and LLC.

The PDI1394P21 normally controls the CTL0–CTL1 and D0–D7

bidirectional buses. The LLC is allowed to drive these buses only

after the LLC has been granted permission to do so by the PHY.

There are four operations that may occur on the PHY-LLC interface:

link service request, status transfer, data transmit, and data receive.

The LLC issues a service request to read or write a PHY register, to

request the PHY to gain control of the serial bus in order to transmit

a packet, or to control arbitration acceleration.

The PHY may initiate a status transfer either autonomously or in

response to a register read request from the LLC.

The PHY initiates a receive operation whenever a packet is received

from the serial bus.

The PHY initiates a transmit operation after winning control of the

serial-bus following a bus request by the LLC. The transmit

operation is initiated when the PHY grants control of the interface to

the LLC.

The encoding of the CTL0–CTL1 bus is shown in Table 7 and

Table 8.

Table 7. CTL encoding when PHY has control of the bus

CTL0

CTL1

NAME

DESCRIPTION

0

0

Idle

No activity (this is the default mode)

0

1

Status

Status information is being sent from the PHY to the LLC

1

0

Receive

An incoming packet is being sent from the PHY to the LLC

1

1

Grant

The LLC has been given control of the bus to send an outgoing packet

Table 8. CTL encoding when LLC has control of the bus

CTL0

CTL1

NAME

DESCRIPTION

0

0

Idle

The LLC releases the bus (transmission has been completed)

0

1

Hold

The LLC is holding the bus while data is being prepared for transmission, or indicating

that another packet is to be transmitted (concatenated) without arbitrating

1

0

Transmit

An outgoing packet is being sent from the LLC to the PHY

1

1

Reserved

None