Page 11
4
4
4. Programming Interface
This chapter contains information needed to write custom software drivers for the
EXM-31. Anyone using the EXM-31 with software compatible with standard PC
modems in general, or specifically a “generic AT&T Class 1 Fax, 14400 Data
Modem” can skip reading this chapter.
The EXM-31defines the following registers in the I/O space (the MSB is the left-
most bit).
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
I/O Port
1 1 0 1 0 0 0 0 100
Device ID Register
Reserved
Interrupt Select
CDEN
102
Configuration Option Byte 1 Register
1
Base Address Select
103
Configuration Option Byte 2 Register
These registers are standard EXM registers for device identification and
configuration. The EXM-31 responds to accesses to these ports only if EXM
expansion interface line -EXMID is asserted. An 8-bit read from I/O address 100h
returns the value D0, the device ID of the EXM-31. Read/write configuration
registers appear at I/O address 102h and 103h. The bit encodings are defined in
chapter 2.
The upper four bits of register 102 are reserved.
Interrupt
selects the interrupt to be generated.
Base address
selects the place in the I/O space in which the 8-byte I/O port area of
EXM-31 appears.
CDEN
specifies whether the EXM is disabled or enabled. If disabled, the EXM will
not respond to any I/O or memory addresses and will not assert an interrupt output; it
will only respond to reads from I/O port 100h and reads and writes from I/O port
102h, and then only if EXM expansion interface line -EXMID is asserted.
Содержание EXM-31
Страница 4: ...EXM 31 Hardware Reference Page iv NOTES ...
Страница 16: ...EXM 31 Hardware Reference Page 8 2 2 NOTES ...
Страница 18: ...EXM 31 Hardware Reference Page 10 3 3 NOTES ...