TMP92CZ26A

92CZ26A-43

3.4 Boot ROM

The TMP92CZ26A contains boot ROM for downloading a user program, and supports two
kinds of downloading methods.

3.4.1 Operation Modes

The TMP92CZ26A has two operation modes: MULTI mode and BOOT mode. The
operation mode is selected according to the AM1 and AM0 pin levels when RESET is
asserted.
(1) MULTI mode: After reset, the CPU fetches instructions from external memory and
executes them.
(2) BOOT mode: After reset, the CPU fetches instructions from internal boot ROM
and executes them. The boot ROM loads a user pro gram into internal
RAM from USB, or via UART, and then branches to the internal
RAM. In this way t he user pro gram starts boot operation. Table 3.4.2
shows an outline of bo ot operation.
Table 3.4.1 Operation Modes
Mode Setting Pins
RESET AM1 AM0 Operation Mode
0 1 MULTI Start from external 16-bit bus memory
1 0 TEST (Setting prohibited)
1 1 BOOT (Start from internal boot ROM)
0 0 TEST (Setting prohibited)
Table 3.4.2 Outline of Boot Operation
Loading
Name Priority Source I/F Destination
Operation after
Loading
(a) 1 PC (UART) UART
(b) 2 PC (USB_HOST) USB Internal RAM Branch to internal
RAM