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PMAC2 User Manual

PMAC2 General Purpose I/O Use 79

PMAC2 GENERAL PURPOSE I/O USE

JIO Port

The JIO port has 32 discrete digital I/O lines for general purpose use. The lines are configurable by byte

for input or output (on the DSPGATE2 I/O IC, the lines are individually configurable for input or output,

but the buffer ICs are only byte-configurable), and individually configurable for inverting or non-

inverting format.

Hardware Characteristics

When configured as an output, each line has a 5V CMOS totem-pole driver. This driver can sink or

source up to 20 mA. There is a 10 kΩ pull-up resistor to 5V on each line for input purposes, but the

driver IC can hold the line high or low despite this resistor. When configured as an input, the buffer IC

presents a high-impedance input either sinking or sourcing; no significant current will flow. The pull-up

resistor on the line will bias the line high in the absence of anything actively pulling the line low at

significantly lower impedance.

Note:

Because all of these lines default to inputs at power-up/reset, any lines to be used

as outputs will pull to +5V at power-up/reset until software configures them as

outputs.

Suggested M-Variables

The 32 I/O lines are memory-mapped into PMAC's address space in registers Y:$C080 and Y:$C081.

Typically these I/O lines are accessed individually with M-variables. Following is a suggested set of M-

variable definitions to use these data lines:

M0->Y:$C080,0 ; I/O00 Data Line; J3 Pin 1

M1->Y:$C080,1 ; I/O01 Data Line; J3 Pin 2

M2->Y:$C080,2 ; I/O02 Data Line; J3 Pin 3

M3->Y:$C080,3 ; I/O03 Data Line; J3 Pin 4

M4->Y:$C080,4 ; I/O04 Data Line; J3 Pin 5

M5->Y:$C080,5 ; I/O05 Data Line; J3 Pin 6

M6->Y:$C080,6 ; I/O06 Data Line; J3 Pin 7

M7->Y:$C080,7 ; I/O07 Data Line; J3 Pin 8

M8->Y:$C080,8 ; I/O08 Data Line; J3 Pin 9

M9->Y:$C080,9 ; I/O09 Data Line; J3 Pin 10

M10->Y:$C080,10 ; I/O10 Data Line; J3 Pin 11

M11->Y:$C080,11 ; I/O11 Data Line; J3 Pin 12

M12->Y:$C080,12 ; I/O12 Data Line; J3 Pin 13

M13->Y:$C080,13 ; I/O13 Data Line; J3 Pin 14

M14->Y:$C080,14 ; I/O14 Data Line; J3 Pin 15

M15->Y:$C080,15 ; I/O15 Data Line; J3 Pin 16

M16->Y:$C080,16 ; I/O16 Data Line; J3 Pin 17

M17->Y:$C080,17 ; I/O17 Data Line; J3 Pin 18

M18->Y:$C080,18 ; I/O18 Data Line; J3 Pin 19

M19->Y:$C080,19 ; I/O19 Data Line; J3 Pin 20

M20->Y:$C080,20 ; I/O20 Data Line; J3 Pin 21

M21->Y:$C080,21 ; I/O21 Data Line; J3 Pin 22

M22->Y:$C080,22 ; I/O22 Data Line; J3 Pin 23

M23->Y:$C080,23 ; I/O23 Data Line; J3 Pin 24

M24->Y:$C081,0 ; I/O24 Data Line; J3 Pin 25

M25->Y:$C081,1 ; I/O25 Data Line; J3 Pin 26

M26->Y:$C081,2 ; I/O26 Data Line; J3 Pin 27

M27->Y:$C081,3 ; I/O27 Data Line; J3 Pin 28