NS9750 - Training

Hardware

PCI-to-AHB Bridge &

PCI Arbiter

PCI-to-AHB Bridge• Provides PCI interface to NS9750• Act as either PCI host or device• Supports PCI 2.1 and 2.2 (specification available at www.pcisig.com)• Support 32-bit PCI mode at 33Mhz max• PCI-to-AHB Address Translation• AHB-to-PCI Address Translation• Supports 6 different memory window sizes on PCI Bus

(256MB,64MB,16MB,4MB,1MB,256KB)• PCI clock to system can be provided by NS9750• Can be configured to provide PCI Central Resource Functions, including

RST#• All AHB to PCI reads done as AHB SPLIT transactions to improve bus

utilization• Cross bridge error detection provided• Supports big or little endian modes on AHB bus.

Internal PCI Arbiter

• Supports up to 3 external PCI masters using PCI arbitration rules

• Rotating priority scheme

• Parks bus on last granted master when bus idle

• Masters that do not start a transaction within 16 PCI Clocks of the bus going idle are considered to be broken and removed from arbitration

PCI Hardware Configuration Pins

• PCI_CENTRAL_RSC_N (Internal pull-down)– “0” -> NS9750 provides PCI Central Resource functions

• RST# driven via NS9750; SERR# input to NS9750

• AD,C/BE and PAR driven low when RST# active

– “1” -> NS9750 does not provide PCI Central functions• RST# configured as input; SERR# configured as output

• AD,CBE, and PAR tri-stated when RST# active

• RTCK (Internal pull-up)– “0” -> Disable internal arbiter

– “1” -> Enable internal arbiter

• BOOT_STRAP[1](Merc-ID)/BP_STAT[0](Merc) (Internal pull-up)– “0” -> CardBus Mode

– “1” -> PCI Mode

PCI System - NS9750 as Host

(Host System)

CONTROL

MERCURY

PCI_CENTRAL_RSC_N2

AD

SERR#

RST#

REQ1#

GNT1#

INTA#

INTB#

INTC#

CONTROL

AD

SERR#

RST#

REQ#

INT#

GNT#

AD[31:0]

CONTROL

SERR#

RST#

REQ#

GNT#

INT#

IDSEL

PCI DEVICE#1

IDSELAD[12]

INTD#

REQ2#

REQ3#

PCI CLKOUT

PCI CLK

IN

PCICLKAD[11]

VCC

VCC

RTCK1

1.RTCK has internal pull-up, so pin can float.2. PCI_CENTRAL_RSC_N has internal pull-down, so pincan float.

Characteristics of Host System

• NS9750 Configuration– Mapped to 256MB PCI space

– PCI Central Resource

– PCI arbiter enabled

– PCI interrupt controller

– PCI Device #0

• System Configuration– Device #1 PCI memory

window mapped to 0xF000_000

– Device #1 PCI IO window mapped to 0x2000_0000

– Device #1 interrupt connected to INTA#

– Device #1 accesses to NS9750 mapped to 0x3000_0000 in NS9750 main memory

– NS9750 PCI window mapped to 0x1000_0000

• Ext Device Configuration– Mapped to 128MB PCI

memory space via BAR0

– Mapped to 64KB PCI IO space via BAR1

– PCI Master/PCI Device #1

– Single interrupt output

Setup of Internal Registers Host System

• Enable REQ# from Device #1 to internal PCI Arbiter

• Enable SERR# interrupt from Device #1

• Enable BAR3 to decode 256MB PCI memory window

• Map accesses to lower 128MB of NS9750’s PCI memory window in AHB space at 0x8000_0000 to Device #1’s PCI memory space at 0xF000_0000.

• Map accesses to lower 64KB of NS9750’s PCI IO window in AHB space at 0xA000_0000 to Device #1’s PCI IO space at 0x2000_0000.

• Map PCI accesses to NS9750 to a 256MB window in NS9750’s main memory at 0x3000_0000

• Enable INTA# interrupt from Device #1 in SCM.

1.See same example of Hardware User’s Guide for more detail.

Setup of Internal Registers Host System

• Initialize NS9750’s BAR3 register so that it responds to a 256MB window at 0x1000_0000 in PCI memory space

• Initialize Device #1’s BAR0 register so that it responds to a 128MB window at 0xF000_0000 in PCI Memory space

• Initialize Device #1’s BAR1 register so that it responds to a 64KB window at 0x2000_0000 in PCI IO space

See same example in Hardware User’s Guide for more detail.

PCI System - NS9750 as Device (Device System)

CONTROL

MERCURY

PCI_CENTRAL_RSC_N1

AD

SERR#

RST#

REQ1#

GNT1#

INTA#

INTB#

INTC#

CONTROL

AD

SERR#

RST#

GNT0#

INTA#

REQ0#

AD

CONTROL

SERR#

RST#

GNT0#

REQ0#

INTA#

PCI Host

IDSELAD[11]

INTD#REQ2#

REQ3#

PCI CLKOUT

PCI CLK

IN

IDSEL AD[12]

RTCK_OUT

VCC

VCC

Notes1. Pin can float because internal pull-down configures tocorrect logic level.

Characteristics of Device System

• NS9750 Configuration– Mapped to 256MB PCI space

via BAR3

– PCI interrupt output

– PCI Device #1

• System Configuration– Host PCI memory window

mapped to 0xF000_000

– Host PCI IO window mapped to 0x2000_0000

– NS9750 interrupt connected to INTA# of Host

– Host accesses to NS9750 mapped to 0x3000_0000 in NS9750 main memory

– NS9750 PCI memory window mapped to 0x1000_0000

– PCI RST# resets entire NS9750 when active

• Ext Host Configuration– Mapped to 128MB PCI

memory space via BAR0

– Mapped to 64KB PCI IO space via BAR1

– PCI Device #0

– Provides PCI arbiter and interrupt controller

– Provides PCI Central Resource Functions

Setup of Internal Registers

for Device System• Program static data in PCI

Configuration Registers per user’s application (e.g.Max_Lat, Min_Gnt, Interrupt Pin)

• Enable BAR3 to decode 256MB PCI memory window

• Map accesses to lower 128MB of NS9750’s PCI memory window in AHB space at 0x8000_0000 to Device #1’s PCI memory space at 0xF000_0000.

• Map accesses to lower 64KB of NS9750’s PCI IO window in AHB space at 0xA000_0000 to Device #1’s PCI IO space at 0x2000_0000.

• Map PCI accesses to NS9750 to a 256MB window in NS9750’s main memory at 0x3000_0000

• NS9750 must be ready for first configuration cycle on bus within 225 PCI clocks after RST# negated per PCI spec

1.See same example of Hardware User’s Guide for more detail.

Setup of Internal Registers

for Device System• Initialize NS9750’s BAR3 register so that it responds to a

256MB window at 0x1000_0000 in PCI memory space• Initialize Device #1’s BAR0 register so that it responds to

a 128MB window at 0xF000_0000 in PCI Memory space• Initialize Device #1’s BAR1 register so that it responds to

a 64KB window at 0x2000_0000 in PCI IO space

See same example in Hardware User’s Guide for more detail.

PCI Burst Read from NS9750

1 2 3 4 5 6 7 8 9 10 11 12 13 14

byte enablescmd

addr data0 data1 data2 data3 data4 data5 data6 data7

pci_clk_in

frame_n

ad[31:0]

cbe_n[3:0]

irdy_n

trdy_n

devsel_n

The functional timing for trdy_n,devsel_n, and the read data on ad[31:0] shows the fastest possible response from the target.

Hints & Kinks

• If NS9750 can generate the PCI CLK, why do I have to connect the PCI_CLK_OUT pin to the PCI_CLK_IN pin?– Since the PCI Bus specification only allows for 2ns of clock skew,

NS9750 must use the same clock signal as the other PCI devices.

• Do I connect the IDSEL pin of NS9750 to the IDSEL pin of all of the other PCI devices? – IDSEL is an input to NS9750 and all of the other PCI devices. It is used

to select a device during PCI configuration cycles. As such, IDSEL of each device must be connected to a unique member of AD[31:11] , where Device #0 is connected to AD[11]; Device #1 is connected to AD[12], etc.

• Since the PCI bus uses reflected-wave switching, do I need to terminate PCI_CLK?– Yes

Hints & Kinks

• When NS9750 is the PCI host, can IDSEL be tied low?– There is no problem with this. However, this prevents any external

devices from accessing NS9750’s PCI configuration registers.

• What PCI pins on NS9750 require external pull-up resistors from the system?– FRAME#,TRDY#,IRDY#,DEVSEL#,STOP#,PERR#,SERR#

– INTA#,INTB#,INTC#, INTD#,REQ1#,REQ2#,REQ3#,

– Any of the GNT[3:1]# signals connected to external PCI devices

• What is the speed of PCI_CLK_OUT when the AHB clock is 100Mhz?– 28.4Mhz See the SCM chapter for a complete table of PCI_CLK_OUT

speed for different AHB clock rates.

Hints & Kinks

• Why does the NS9750 not retry target reads to it that take in excess if 32 PCI clocks to complete? – The PCI 2.2 specification states that a host bus bridge must issue a retry if

it cannot return the data within 32 PCI clocks from the assertion of FRAME#. The PCI interface to NS9750 holds the PCI bus until the data is returned instead. In a 2 device PCI system (i.e. NS9750 and 1 external device), this is a non-issue. In a more complex system, this would prevent traffic between external devices until NS9750 returns the read data.