pc87317vul National Semiconductor Corporation, pc87317vul Datasheet - Page 150

• Manufacturer Part Number: pc87317vul
• Description: Pc87317vul/pc97317vul Superi/o Plug And Play Compatible With Acpi Compliant Controller/extender
• Manufacturer: National Semiconductor Corporation

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Bits 1,0 - DMA Channel Select
Bit 2 - Reserved
Bits 5-3 - Interrupt Select Bits
Bit 6 - IRQ Signal Value
Bit 7 - Reserved
6.5.12 Extended Control Register (ECR)
This register controls the ECP and parallel port functions. On
reset this register is initialized to 00010xx1 (bits 1 and 2 de-
pend on the clock status). IOCHRDY is driven low on an ECR
read when the ECR status bits do not hold updated data.
Bit 1 Bit 0
0
0
1
1
These bits reflect the value of bits 1,0 of the PP Config0
register (second level offset 05h). Microsoft’s ECP Pro-
tocol and ISA Interface Standard defines these bits as
shown in TABLE 6-7 "ECP Mode DMA Selection".
Bits 1,0 of PP Config0 are read/write bits, but CNFGB
bits are read only.
Upon reset, these bits are initialized to 00.
This bit is reserved and is always 0.
These bits reflect the value of bits 5-3 of the PP Config0
register at second level index 05h. Microsoft’s ECP Pro-
tocol and ISA Interface Standard defines these bits as
shown in TABLE 6-8 "ECP Mode Interrupt Selection".
Bits 5-3 of PP Config0 are read/write bits, but CNFGB
bits are read only.
Upon reset, these bits have undefined values.
This bit holds the value of the IRQ signal configured by
the Interrupt Select register (index 70h of this logical de-
vice).
This bit is reserved and is always 0.
Bit 5
TABLE 6-8. ECP Mode Interrupt Selection
0
0
0
0
1
1
1
1
TABLE 6-7. ECP Mode DMA Selection
0
1
0
1
Bit 4
0
0
1
1
0
0
1
1
8-bit DMA selected by jumpers. (Default)
Bit 3
0
1
0
1
0
1
0
1
DMA channel 1 selected.
DMA channel 2 selected.
DMA channel 3 selected.
DMA Configuration
Selected by jumpers.
Interrupt Selection
IRQ10 selected.
IRQ11 selected.
IRQ14 selected.
IRQ15 selected.
IRQ7 selected.
IRQ9 selected.
IRQ5 selected.
Parallel Port (Logical Device 4)
150
Bit 0 - FIFO Empty
Bit 1 - FIFO Full
Bit 2 - ECP Interrupt Service
0
7
This bit continuously reflects the FIFO state, and there-
fore can only be read. Data written to this bit is ignored.
When the ECP clock is frozen this bit is read as 1, re-
gardless of the actual FIFO state.
0: The FIFO has at least one byte of data.
1: The FIFO is empty or ECP clock is frozen.
This bit continuously reflects the FIFO state, and there-
fore can only be read. Data written to this bit is ignored.
When the ECP clock is frozen this bit is read as 1, re-
gardless of the actual FIFO state.
0: The FIFO has at least one free byte.
1: The FIFO is full or ECP clock frozen.
This bit enables servicing of interrupt requests. It is set
to 1 upon reset, and by the occurrence of interrupt
events. It is set to 0 by software.
While this bit is 1, neither the DMA nor the interrupt
events listed below will generate an interrupt.
While this bit is 0, the interrupt setup is “armed” and an
interrupt is generated on occurrence of an interrupt
event.
While the ECP clock is frozen, this bit always returns a
0 value, although it retains its proper value and may be
modified.
When one of the following interrupt events occurs while
this bit is 0, an interrupt is generated and this bit is set
to 1 by hardware.
— DMA is enabled (bit 3 of ECR is 1) and terminal
— FIFO write threshold reached (no DMA - bit 3 of ECR
— FIFO read threshold reached (no DMA - bit 3 of ECR
0
6
count is reached.
is 0; forward direction (bit 5 of DCR is 0), and there
are eight or more bytes free in the FIFO).
is 0; read direction set - bit 5 of DCR is 1, and there
are eight or more bytes to read from the FIFO).
0
ECP Mode Control
5
FIGURE 6-26. ECR Register Bitmap
1
4
ECP Interrupt Mask
0
3
ECP DMA Enable
2
ECP Interrupt Service
1
FIFO Full
1
0
Reset
Required
FIFO Empty
Extended Control
Register (ECR)
Offset 402h