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Diffstat (limited to 'src/devices/cpu/tms9900/tms99com.h')
-rw-r--r--src/devices/cpu/tms9900/tms99com.h19
1 files changed, 12 insertions, 7 deletions
diff --git a/src/devices/cpu/tms9900/tms99com.h b/src/devices/cpu/tms9900/tms99com.h
index 6495ada9133..02cc729263d 100644
--- a/src/devices/cpu/tms9900/tms99com.h
+++ b/src/devices/cpu/tms9900/tms99com.h
@@ -13,11 +13,14 @@
TI990/12 Multi-chip implementation, faster than 990/10. Huge instruction set
TMS9900 Mono-chip implementation, 1976. Used in the TI-99/4(A) computer.
+ No mapper, no privileged mode.
TMS9940 Microcontroller with 2kb ROM, 128b RAM, decrementer, CRU bus, 1979
- TMS9980 8-bit variant of tms9900. Two distinct chips actually : tms9980a
- and tms9981 with an extra clock and simplified power supply
+ TMS9980 like TMS9900, but with integrated 16/8 databus multiplexer,
+ smaller address/cru space, and simplified interrupt input.
+ Two distinct chips actually: tms9980a, and tms9981 with an
+ extra clock and simplified power supply
TMS9985 9940 with 8kb ROM, 256b RAM, and a 8-bit external bus, c. 1978 (never released)
@@ -25,8 +28,9 @@
SBP68689 Improved 9989, built as an ASIC as 9989 was running scarce
- TMS9995 TMS9985-like, with many improvements (but no ROM). Used in the
- TI-99/8 prototype and the Geneve computer.
+ TMS9995 TMS9985-like, with many improvements (but no ROM). Used in
+ some arcade systems, in the TI-99/2 and TI-99/8 prototype,
+ and in the Geneve computer.
TMS99000 Improved mono-chip implementation, meant to replace 990/10, 1981
TMS99105 This chip is available in several variants which are similar
@@ -65,9 +69,10 @@ enum
};
/*
- We are using setaddress this way: The address is the object to be
- written; as address we use the values of the DBIN and IAQ lines. That
- means we do not need separate dbin and iaq setting methods.
+ These values represent line states for bus control lines. In a setaddress
+ operation, the current state of the address bus lines is represented
+ by the address where these values are written to. The callee should check
+ the values to find out whether a read or write operation will follow.
*/
enum
{