NEC Network Controller uPD98502 - Manual (Page 404)

CHAPTER 7 PCI CONTROLLER
404 Preliminary User’s Manual S15543EJ1V0UM
7.5.19.4 Command register
This register provides coarse control over a device’s ability to generate and respond to PCI cycles. This register is
valid in Host-mode. The V R 4120A should set the register.
R/W Bits Field
Internal
bus
PCI
Default Description
15:10 Reserved R R 0 Hardwired to ‘0’s.
9 Fast Back-to-
Back Enable
R R 0 Hardwired to a ‘0’, because the PCI Controller cannot generate
fast back-to-back transaction.
8 System Error
Enable
R/W R/W 0 This bit is an enable bit for the SERR_B driver. ‘1’ enables the
SERR_B driver.
7 Wait Cycle
Enable
R R 0 Hardwired to a ‘0’, because the PCI Controller does not use
address/data stepping as PCI-device.
6 Parity Error
Response
R/W R/W 0 This bit controls the PCI Controller’s response to parity errors.
When the bit is set to a ‘0’, the PCI Controller must take its normal
action if a parity error is detected. When the bit is set to a ‘1’, the
PCI Controller sets its Detected Parity Error status bit (bit15 in the
Status register) if an error is detected, but does not assert
PERR_B and continues normal operation.
5 VGA Palette
Snoop Enable
R R 0 Hardwired to a ‘0’, because the PCI Controller does not have
VGA function.
4 Memory Write
and Invalidate
Enable
R/W R/W 0 This is an enable bit for using the Memory Write and Invalidate
command. When this bit is set to a ‘1’, the PCI Controller can
generate the Memory Write and Invalidate command. When it is a
‘0’, Memory Write is used and Memory Write and Invalidate
command is not issued.
3 Special Cycle
Recognition
R R 0 Hardwired to a ‘0’, because the PCI Controller dose not respond
to Special Cycle operations.
2 Bus Master
Enable
R/W R/W 0 Controls The PCI Controller’s ability to act as a master on the PCI
bus. ‘0’ disables the PCI Controller from generating PCI
accesses. ‘1’ allows the PCI Controller to behave as a bus
master.
1 Memory Access
Enable
R/W R/W 0 Controls a device’s response to Memory Space accesses. ‘0’
disables The PCI Controller’s response. ‘1’ allows the PCI
Controller to respond to Memory space accesses.
0 I/O Access
Enable
R R 0 Hardwired to ‘0’, because the PCI Controller does not issue the
I/O space.