Heidenhain IK320 Encoder Setup

Author: Kurt Goetze (goetze@aps.anl.gov)

Table of contents

• Supported Record Types
• IK320card.db Configuration
  • Calculating the switches value
  • VME Address Calculation
  • IRQ level
  • J3 Jumper
• IK320group.db Configuration

The Heidenhain IK320 is a VME counter/interpolator for linear and angular encoders. This page describes how to configure the IK320 for use with EPICS (synApps). The IK320 device support and driver were written by Till Straumann of PTB at BESSY.

The IK320 builds on both vxWorks and RTEMS.

Supported Record Types

Record Type	DTYP	Purpose
mbbo	Heidenhain IK320 Command	Function command (e.g., read, reference search)
mbbo	Heidenhain IK320 Direction	Counting direction
mbbo	Heidenhain IK320 X3 Mode	X3 interpolation mode
stringout	Heidenhain IK320 Param	Parameter get/set
ai	Heidenhain IK320	Single-axis reading
ai	Heidenhain IK320 Group	Group trigger reading

IK320card.db Configuration

Here is an example of a record from the IK320card.db database:

record(mbbo, "$(P)IK320:$(sw2)$(axis)function")
{
    field(DTYP, "Heidenhain IK320 Command")
    field(OUT,  "#C$(switches) S$(irq) @$(axis)")
}

Here is an example of loading IK320card.db in the startup command file:

dbLoadRecords("$(VME)/vmeApp/Db/IK320card.db", "P=kag:,sw2=card0:,axis=1,switches=41344,irq=3")

The macros that need additional explanation are $(switches) and $(irq).

Calculating the switches value

The switches argument is derived by taking the hexadecimal value of the S1/S2 switch banks and converting it to decimal. A switch in the OFF position is a 1.

For example:

Switch S1               Switch S2
---------               ---------
1000 0101               0000 0001
        ^- MSB                  ^- MSB

Rewriting in conventional notation (MSB on the left):

S1: 1010 0001 = 0xA1
S2: 1000 0000 = 0x80

Combined: 0xA180 = 41344 (decimal), hence switches=41344 in the dbLoadRecords() call above.

VME Address Calculation

The IK320 occupies space in both the A16 and A24 VMEbus address spaces. The formulas for determining the addresses based on the switch settings are:

A24 base address:

A24 base = 0x00C00000 + (0x4000 * S2)

In the example above, S2 = 0x80:

A24 base = 0x00C00000 + (0x4000 * 0x80) = 0xE00000

A16 base address:

A16 base = (S1 & 0xE0) * 0x100

In the example above, S1 = 0xA1:

A16 base = (0xA1 & 0xE0) * 0x100 = 0xA0 * 0x100 = 0xA000

IRQ level

The irq value should be the IRQ level set by jumpers J1 and J2 on the IK320 board. According to the manual, these levels must be the same. Typically they are left at the factory default of 3.

J3 Jumper

Most VME CPUs do not support the ADO cycle. It is recommended that J3 be jumpered to generate a DTACK, per page 14 of the IK320 manual. For a group of IK320 boards, one of the boards should have J3 jumpered.

IK320group.db Configuration

Here is an example of loading IK320group.db in the startup command file:

dbLoadRecords("$(VME)/vmeApp/Db/IK320group.db", "P=kag:,group=5")

In order to use more than one channel, even if it is on the same board, a copy of the IK320group.db database must be loaded. This database contains one AI record that must be processed in order for readings to be taken. The $(group) macro is derived by taking the decimal value of bits 8, 7, and 6 on S1. For example, if these bits were set to 1 0 1, then group=5.