3

PCCchip2

SCC Receive Interrupt Control Register

ADR/SIZ

 

 

 

 

 

$FFF4201F (8 bits)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BIT

7

 

6

 

5

 

4

3

 

2

1

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NAME

SC1

 

SC0

 

IRQ

 

IEN

AVEC

 

IL2

IL1

 

IL0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

OPER

R/W

 

R/W

 

R

 

R/W

R/W

 

R/W

R/W

 

R/W

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RESET

0 PL

 

0 PL

 

X

 

0 PL

0 PL

 

0 PL

0 PL

 

0 PL

 

 

 

 

 

 

 

 

 

 

 

 

IL2-IL0

 

Interrupt Request Level. These three bits select the

 

 

 

 

interrupt level for SCC Receive Interrupt. Level 0 does

 

 

 

 

not generate an interrupt.

 

 

 

 

 

AVEC

 

When this bit is high, the PCCchip2 supplies the interrupt

 

 

 

 

vector to the MPU during an IACK for SCC receive

 

 

 

 

interrupt. When this bit is low, the PCCchip2 obtains the

 

 

 

 

vector from the SCC and passes it to the MPU. The use of

 

 

 

 

the AVEC mode is not recommended.

 

 

 

 

IEN

 

Interrupt Enable. When this bit is high, the interrupt is

 

 

 

 

enabled. The interrupt is disabled when this bit is low.

 

IRQ

 

Interrupt Status. This status bit reflects the state of the

 

 

 

 

SCC-IRQ3 pin of the CD2401 (qualified by the IEN bit).

 

 

 

 

When this bit is high, an SCC receive interrupt is being

 

 

 

 

generated at the level programmed in IL2-IL0 (if

 

 

 

 

 

nonzero). This status bit does not need to be cleared,

 

 

 

 

because it is not edge-sensitive.

 

 

 

 

 

SC1-SC0

 

Snoop Control. These control bits determine the value that

 

 

 

 

the PCCchip2 drives onto the local MC68040 bus SC1

 

 

 

 

and SC0 pins, when the CL-CD2401(SCC) performs

 

 

 

 

DMA accesses. During SCC DMA, when bit SC0 is 0,

 

 

 

 

Local Bus pin SC0 is low, and when bit SC0 is 1, pin SC0

 

 

 

 

is high. The same relationship holds true for bit and pin

 

 

 

 

SC1. See the M68040 and MC68060 user’s manuals for

 

 

 

 

details on how it uses the Snoop Control signals.

 

Note On the MVME177P, which uses only SC1, the SC0 bit must be 0.

3-30

Computer Group Literature Center Web Site

Page 228
Image 228
Motorola MVME1X7P manual SCC Receive Interrupt Control Register