3

PCCchip2

SCC Modem Interrupt Control Register

ADR/SIZ

 

 

 

 

$FFF4201D (8 bits)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

BIT

23

22

 

21

 

20

 

19

 

18

17

 

16

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NAME

 

 

 

IRQ

 

IEN

 

AVEC

 

IL2

IL1

 

IL0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

OPER

R

R

 

R

 

R/W

 

R/W

 

R/W

R/W

 

R/W

 

 

 

 

 

 

 

 

 

 

 

 

 

 

RESET

0

0

 

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 modem 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 modem

 

 

 

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-IRQ1 pin of the CD2401 (qualified by the IEN bit).

 

 

 

When this bit is high, an SCC modem 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.

 

 

 

 

3-28

Computer Group Literature Center Web Site

Page 226
Image 226
Motorola MVME1X7P manual SCC Modem Interrupt Control Register, Avec, Irq