Delta Tau GEO BRICK LV User Manual
Turbo PMAC User Manual
Turbo PMAC General Purpose I/O Use
197
Turbo PMAC2 General-Purpose I/O (JIO) Port
The JIO port on a Turbo PMAC2 (on Acc-5E for a UMAC Turbo) 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.
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 k
source up to 20 mA. There is a 10 k
Ω 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.
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.
as outputs will pull to +5V at power-up/reset until software configures them as
outputs.
Suggested M-Variables
Note:
In a UMAC Turbo system, it is possible to have the DSPGATE2 IC driving the
JIO port at a base address other than the standard $078400. However, this is
unlikely, so the following discussion assumes the standard base address of
$078400 for this IC.
JIO port at a base address other than the standard $078400. However, this is
unlikely, so the following discussion assumes the standard base address of
$078400 for this IC.
The 32 I/O lines are memory-mapped into PMAC’s address space in registers Y:$078400 and Y:$078401.
Typically these I/O lines are accessed individually with M-variables. A complete list of the suggested M-
variables is shown in the Software Reference; a few are shown here:
Typically these I/O lines are accessed individually with M-variables. A complete list of the suggested M-
variables is shown in the Software Reference; a few are shown here:
M0->Y:$078400,0
; I/O00 Data Line; J3 Pin 1
M1->Y:$078400,1
; I/O01 Data Line; J3 Pin 2
…
M23->Y:$078400,23
; I/O23 Data Line; J3 Pin 24
M24->Y:$078401,0
; I/O24 Data Line; J3 Pin 25
M25->Y:$078401,1
; I/O25 Data Line; J3 Pin 26
…
M31->Y:$078401,7
; I/O31 Data Line; J3 Pin 32
Direction Control
The direction control bit for each of these I/O bits is in the corresponding bit in the matching X register.
For example, the direction control bit for I/O03 is located at X:$078400,3; the direction control bit for
I/O30 is located at X:$078401,6. Because the buffer ICs can be switched only by byte, it is best to define
8-bit M-variables for the direction control. Suggested definitions are:
For example, the direction control bit for I/O03 is located at X:$078400,3; the direction control bit for
I/O30 is located at X:$078401,6. Because the buffer ICs can be switched only by byte, it is best to define
8-bit M-variables for the direction control. Suggested definitions are:
M32->X:$078400,0,8
; Direction control for I/O00 to I/O07
M34->X:$078400,8,8
; Direction control for I/O08 to I/O15
M36->X:$078400,16,8
; Direction control for I/O16 to I/O23
M38->X:$078401,0,8
; Direction control for I/O24 to I/O31
These M-variables should take values of 0 or 255 ($FF) only; 0 sets the byte to input, 255 sets the byte to
output.
output.