PCI6620 datasheet(71/160 Pages) TI

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4–5

Table 4–3. Command Register Description (continued)

BIT

SIGNAL

TYPE

FUNCTION

MEM_EN

Memory space enable. This bit controls whether or not the PCI6x20 device can claim cycles in PCI memory

space.

0 = Disables the PCI6x20 response to memory space accesses (default)

1 = Enables the PCI6x20 response to memory space accesses

IO_EN

I/O space control. This bit controls whether or not the PCI6x20 device can claim cycles in PCI I/O space.

0 = Disables the PCI6x20 device from responding to I/O space accesses (default)

1 = Enables the PCI6x20 device to respond to I/O space accesses

4.5

Status Register

The status register provides device information to the host system. Bits in this register can be read normally. A bit

in the status register is reset when a 1 is written to that bit location; a 0 written to a bit location has no effect. All bit

functions adhere to the definitions in the PCI Bus Specification, as seen in the bit descriptions. PCI bus status is shown

through each function. See Table 4–4 for a complete description of the register contents.

Bit

Name

Status

Type

Default

Status

Offset:

06h (Functions 0, 1)

Type:

Read-only, Read/Write

Default:

0210h

Table 4–4. Status Register Description

BIT

SIGNAL

TYPE

FUNCTION

15 ‡

PAR_ERR

Detected parity error. This bit is set when a parity error is detected, either an address or data parity error.

Write a 1 to clear this bit.

14 ‡

SYS_ERR

Signaled system error. This bit is set when SERR is enabled and the PCI6x20 device signaled a system error

to the host. Write a 1 to clear this bit.

13 ‡

MABORT

Received master abort. This bit is set when a cycle initiated by the PCI6x20 device on the PCI bus has been

terminated by a master abort. Write a 1 to clear this bit.

12 ‡

TABT_REC

Received target abort. This bit is set when a cycle initiated by the PCI6x20 device on the PCI bus was

terminated by a target abort. Write a 1 to clear this bit.

11 ‡

TABT_SIG

Signaled target abort. This bit is set by the PCI6x20 device when it terminates a transaction on the PCI bus

with a target abort. Write a 1 to clear this bit.

10–9

PCI_SPEED

DEVSEL timing. These bits encode the timing of DEVSEL and are hardwired to 01b indicating that the

PCI6x20 device asserts this signal at a medium speed on nonconfiguration cycle accesses.

8 ‡

DATAPAR

Data parity error detected. Write a 1 to clear this bit.

0 = The conditions for setting this bit have not been met.

1 = A data parity error occurred and the following conditions were met:

a. PERR was asserted by any PCI device including the PCI6x20.

b. The PCI6x20 device was the bus master during the data parity error.

c. The parity error response bit is set in the command register.

FBB_CAP

Fast back-to-back capable. The PCI6x20 device cannot accept fast back-to-back transactions; thus, this bit

is hardwired to 0.

UDF

UDF supported. The PCI6x20 device does not support user-definable features; therefore, this bit is

hardwired to 0.

66MHZ

66-MHz capable. The PCI6x20 device operates at a maximum PCLK frequency of 33 MHz; therefore, this

bit is hardwired to 0.

‡ One or more bits in this register are cleared only by the assertion of GRST.

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