z90102 ZiLOG Semiconductor, z90102 Datasheet - Page 20

• Manufacturer Part Number: z90102
• Description: 40-pin Low-cost Digital Television Controller
• Manufacturer: ZiLOG Semiconductor

FUNCTIONAL DESCRIPTION (Continued)
Z90102/90103/90104
40-Pin Low-Cost Digital Television Controller
Stack. Either the internal register file or the external data
memory is used for the stack. An 8-bit Stack Pointer is
used for the internal stack that resides within the 236 gen-
eral-purpose registers.
Counter/Timers. There are two 8-bit programmable
counter/timers (T0-T1), each driven by its own 6-bit pro-
grammable prescaler (PRE0 and PRE1). The T1 prescaler
can be driven by internal or external clock sources; howev-
20
TIN
Clock
Logic
OSC
P31
External Clock
Internal Clock
Gated Clock
Triggered Clock
Internal
Clock
¸4
Figure 18. Counter/Timer Block Diagram
¸4
Write
Write
Initial Value
Initial Value
Register
Register
Counter
Counter
PRE0
PRE1
Down
Down
6-Bit
6-Bit
er, the T0 prescaler is driven by the internal clock only (Fig-
ure 18).
The counter, but not the prescalers, are read at any time
without disturbing their value or count mode. The clock
source for T1 is user definable and is the internal micropro-
cessor clock (XTAL clock/4), or an external signal input
through Port 3, P31. The counter/timers are programmably
cascaded by connecting the T0 output to the input of T1.
Write
Internal Data Bus
Write
Internal Data Bus
Initial Value
Initial Value
Register
Register
Counter
Counter
Down
Down
8-Bit
8-Bit
T0
T1
¸2
Read
Read
Current Value
Current Value
Register
Register
T0
T1
Serial I/O
Clock
TOUT
P36
IRQ5
IRQ4
DS97TEL1902
Zilog