MAP ROM (contents of Z21, the MMI 6331 IJ or N82S123N)
------- 
                 +-------- BASIC 0000-1FFF ROM
                 |  +----- BASIC 2000-2FFF ROM
                 |  |  +-- BOOT ROM
Addr    Cont    B0 B2 Bt 
                 1  2  3
00000   F7       1  1  1
00001   F7       1  1  1
00010   F7       1  1  1
00011   F3       1  1  0  Boot on 
00100   F7       1  1  1
00101   F7       1  1  1
00110   F3       1  1  0  Boot ROM on 0000-07FF (RESET)
00111   F7       1  1  1
01000   F7       1  1  1
01001   F7       1  1  1
01010   F7       1  1  1
01011   F3       1  1  0  Boot ROM on 0000-07FF, BASIC*
01100   F7       1  1  1
01101   F7       1  1  1
01110   F3       1  1  0  Boot ROM on 0000-07FF,BASIC*, addr 0000-0?FF
01111   F7       1  1  1
10000   F7       1  1  1
10001   F7       1  1  1
10010   F7       1  1  1
10011   F3       1  1  0  Boot ROM on 3000-37FF
10100   F7       1  1  1
10101   F5       1  0  1  Basic ROM 2 active on 2000-2FFF
10100   F6       0  1  1  Basic ROM 1 active on 0000-1FFF ??
10101   F7       1  1  1
10110   F7       1  1  1
10111   F7       1  1  1
11000   F7       1  1  1
11001   F7       1  1  1
11010   F7       1  1  1
11011   F3       1  1  0  Boot ROM on CPM, E000 - E7FF
11100   F7       1  1  1
11101   F7       1  1  1
11110   F7       1  1  1
11111   F7       1  1  1



VIDEO = (3C00 ./. 3FFF), D3*  + (F800 ./. FFFF).D3
KEYB  = (3800 ./. 3BFF), D3*  + (F400 ./. F7FF).D3
OE*   = (3000 ./. 37FF), D3*  + (EC00 ./. F3FF).D3
ROM*  = (37E0 ./. 37EF), excl + (EFE0 ./. EFEF).excl

Description of PORT 254 (FEh)

bit 1 : CPU clock; 0 = 1.77 MHz, 1 = 3.54 MHz
bit 2 : BOOT ROM active; 0 = BOOT ROM not at 0000h-07FFh, 1 = BOOT ROM at 0000h-07FFh
bit 3 : BASIC active; 0 = BASIC active, 1 = BASIC inactive (RAM at 0000h-2FFFh)
bit 4 : MEMORYMAP; 0 = TRS-80 mode, 1 = CP/M mode
bit 5 : HALT operation; 0 = HALT* generates NMI*, 1 = HALT* stops CPU
bit 6 : Memory Mapped devices; 0 = Memory Mapped devices active, 1 = only RAM in memory
bit 7 : -
bit 8 : -