Idle curiousity, does anyone happen to know whether the TMS4100 ROM
was a standard off-the-shelf character generator from TI, or was it a
generic mask-ROM-to-customer-order, or otherwise have data on it such
as it's native size.
The 1976 'Memroy and Microprocessor Databook' (Texas Instruemnts) lists a
TMS4102 Cheracter Gerneator. Like the one in the HP9830, it reads out a
column at a time, and has the same pinout. I will give the pinout fro
mthe databook in a minute. The difference seems to be that the TMS4103
is specified as having 'Inputs and Outputs Fully TTL compatible) while
the inputs o ntne TMS4100 seem to be 12V levels. The HP9830 Dispaly
Driver PCB (09830-66542) drives them with high voltabge open-collector
buffers ('145 and '07), pulled up to 12V via a 1k2 resistor.
Anyway, the pinout of the TMS4103 (and I used this when
reverse-engineering the HP9830) is :
-----
O1 -| U |- I7
NC -| |- I1
O2 -| |- I2
NC -| |- I3
O3 -| |- I4
NC -| |- I5
O4 -| |- CE
NC -| |- CD
O5 -| |- CC
NC -| |- CB
O6 -| |- CA
NC -| |- Vss
O7 -| |- I6
Vdd -| |- Vgg
-----
Where : I1-I6 = Binary-encoded chracter inputs (64 different chracters)
I7 = Chip eneable input (active high)
CA-CE = Column select inputs, 1-of-5 encoded
O1-O7 = Data output
Vdd,Vss,Vgg = power/ground/bias
Unforutnately there is only 1 page of data on it in the book and it
doesn't give the paterns for the characters. The data sheet is dated May
1975 (after hte design of the HP9830, of course).
Full id:
TMS4100
ZA 5705
T-04163
7308 <-- date code
It's the character generator in the HP9830, arranged for character
column scanning order rather than row scanning (7-bits columns at the
outputs rather than 5-bit rows).
I see three possibilities:
- the TI TMS4100 is a character generator ROM
- it's a TI TMS 4100 mask ROM, programmed and sold by TI as a
character gen
- it's a TI TMS 4100 mask ROM, programmed to order for HP
My _guess_ is that the TMS4100 is a standrd character generator ROM and the
TSM4103 is an imporved version with TTL-compatible inputs.
The ratehr odd address inpout (1-of-5 colum select, for example) seems to
suggst it's not a standard ROM device (I would epxpect fully bianry coded
address inputso n such a device).
If yuo need to replace it, do watch for those 12V levels. it's very easy
to covert abck to 5V levels, (jsut change where the pull-ups go to) but you
may not want to make too many changes to the board.
-tony