Maxim Integrated Secure Microcontroller - Manual (Page 14)

Secure Microcontroller User’s Guide
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Scratchpad Registers
Scratchpad registers are 128 registers where data can be stored directly. They are addressed from 00H to
7FH and can be accessed by a MOV instruction. Included in the scratchpad area are four 8-byte banks of
working registers. These registers are not part of the data memory map.
Serial I/O
The on-chip serial I/O port is composed of a receive data buffer, a transmit data buffer, and a control
register. Both the receive data buffer and the transmit data buffer are accessed in a single location (SBUF)
in the SFR map. The control register (SCON) is accessed in a separate location. When the serial I/O
function is enabled, two external I/O pins (P3.0, P3.1) are reassigned in hardware to serve the transmit
and receive data functions.
Programmable Timers
Two 16-bit programmable timers are included that can perform various timing and counting functions.
Four registers (TH1, TL1, TH0, and TL0) access the upper and lower halves of each of the two
timer/counters. A single control register (TCON) is used to select the various operating modes of the two
timers. Two external I/O pins (P3.4, P3.5) can be programmed to serve as external counter inputs, one pin
for each of the two timer/counters.